236 BULLETIN OF THE UXITED STATES

236 BULLETIN OF THE UXITED STATES

FISH COMMISSION.

THE E'KOTOKOA

ASfD

PKOTOPBIYTES

COrt^J^IDERED

AS TME PRI-

MAfieV

OB

IIVI>SRE(1;T

^OrJS€E OF

GTEIE FOOS>

OF

F1SI2ES.

By ^JTOMW

^A.

RYOER.

lu the course of observations

made

_during tlie last few _{years the} writerhasbeen

more and more

_Impressed with theimportance ^of the Protozoa

and

Protophytes ^asan indirector primary ^{source of}

much

of the food

consumed by

^{man. Thisis} notably^{true of}

what

is

known

as fish

and

shell-fishfood.

As

_{verystriking-}instances of thetruth ofthese propositions,

we

need _onlyto allude to thevarious edible species of the herring family, the shad, herring, and _sardine, the gill-rakers of which aremodified soas toenable

them

to strain theminute_living or-

ganisms^{out of the} water which is passed through ^the

mouth

in _resjn- ration; the

menhaden

or Brevoortia, which is of the

same

_family

and swarms

_{along ourcoast,}

and

whichinits turn furnishes a_largepropor- tionof itsfood tothe edible blueflsh,

and

so serves this tyrant^of the sea asa_strainer,elaborator,

and

accumulator,^asitwere, ofthe minuter

lifeofthe oceanic wastes whichit inhabits.

The

_oyster,in likemanner, subsisting, as^it does, entirely u])ou Protozoa, Diatoms, minute ^ciliated

larvie, &c., reminds us_forciblythat for

some

of themost _savory lux- uries ofthe table

we

are indirectlyindebted tothe existence of count- less hosts_{of living}marine _beings, which can be rendered visibleonly with _{the help} ofa microscope.

Comparatively few^fishes appear ^to be able to utilizethe protozoa directly as asourceof food.

The

most remarkable _exception to this rule

was

first

made known _by

Professor S. A. _Forbes, of_Illinois,

who

found the intestiues of certain

young

^{suckers or} Catostomidm packed withthe shells or tests of difilugian rliizopods. In the Proceedings ^of the

Academy

^{of Natural Sciences of} Philadelphia ^for 1881, Professor Leidy ^{states that}

upon

examining two ^slides containing

some

of tho intestinalcontents of

young

Mijxostoma macrolepidotum and Erimyzon sucetta submitted to

him

for exandnation by ^ProfessorForbes he

was

able to distinguishthe shellsof six distinct species of rhizo])ods or ^test- coveredamoeboid Protozoa.

The

habits of the fishes in question are,

however,mud-loving, and, ^since they ^are provided^{with a}

more

orless suctorial mouth, ^{it is} easy^to understand

how

_{they might} readily con-

sume

_large

numbers

of these Protozoanswherethe surfaceof the ooze of the bottoms of the streams and _pools inhabited by ^the fishes

was

favorableto the ]iropagation and _healthy existence oftheformer.

Inorderto render the vast multitude of Protozoa available as fish-

foodit is necessary that they be

consumed

_{by larger organisms, which}

in theirturn

may

^be

^consumed

bj^thefishes.

Upon

investigating the literature relating^to the foodof the smallercrustaceans, especially of the Entomostraca which enterso largely intothe food supplies of most

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

237

younnf^fishes and _very

many

adult forms, ^{I find} tbat thealmost unani-

mous

testimony ^ofvarious observers isto theeffect that thesecreatures are _larg^elycarnivorous,

and

subsistmostly

upon

protozoa, or thelow- est grade ^of animal existence. In proof^ofthe_foregoing, the following extracts are here introduced.

lu his Natural History ^of the Biitish Entomostraca, page ^{of the} introduction, Dr.

W.Baird

remarks: ^"Ihave no doubt thatmost ofthe entomostraca are essentiallycarnivorous,

and

I have frequently seen specimensof CyrrHs in their turn, assoonas dead, attackedimmediately

bj'quantities of Cyclops quadricornis, which inafew minutes hadfast-

ened themselves _uijon the dead _animal,

and

were so intent upon ^their prey ^thattheywere _{scarcely frightened}

away

^fromit

by

being touched with a brush. In a short time the _Cypris might ^{be seen} lying at the bottom of the vessel, the valvesof the shell separated and emptied ^of

its contents. Leeuweidioek

and

I>e Geer not only maintain that the Cydops quadricornis^livesuponanimalcules, butthatiteven_preys

upon

its

own

_young, afactwhichIhave also noticed_myself. Jurineasserts that the Cyclops quadricornis ^is carnivorous from _taste,

and

_only her- bivorousfrom _necessity; while the

Daphnia

ptdex^he_{distinctly affirms,}

livesupon animalcules. Place a few Entomostraca, ^{such, for} example, as the Dapliiiia', Chirocephali, Lyncei, «&c., in a vessel with pure, clear water, and _only

some

_A'egetable matters in _it,

and

they gradually^be-

come

_languid, transparent,

and

_{finally die;} but

mix

with this water some which contains

numerous

_Infusoria,

and

the Entomostraca will thenbe seen speedily^to assume another _aspect.

They become

lively

and

_active,andthe opacity^{of their}alimentary canaltestifies sufficiently the cause of it.

When,

indeed,

we

consider the amazingquantity ^of animals which

swarm

ⁱⁿ ourponds andditches,and the deterioration of the surrounding atmosphere which might ensue fromthe putrefaction of theirdead bodies,

we

see adecided fitness in these Entomostraca beingcarnivorous, thusheli)ing to prevent the noxious^{effects of}putrid airwhich might ^otherwise ensue_; whilst they^{in their} turn

become

a prey ^tootheranimals which, no doubt, serve^theirpurposes ^{also in}the economy ^of nature."

"The

food of the Lynceidw,''^ says Baird, "consists of both animal and vegetable matter, and while they prey upon animalcules smaller than themselves, they, in their turn, aredevoured in great

numbers by

insects larger than_theyare."

According^to Pritchard, the Chyodorussphaericus^is thechoicefoodof a species of fresh-water Nais which hecalls Lurco.

"So

_great is the voracity,"he _says,"ofthiscreaturetliat I haveseen a middle-sized one devour seven _Lynceiin halfanhour."

Referring ^to the DapJiniada', our author again observes:

"The

food of these animals, according to Straus, consists of vegetable matter,

and

not animal

; but Ihave found thatof

two

_{groups placed} in se])arate vessels of clear water, theone ha^ingonlyparticlesof vegetable matter

238 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

placed beside tliem, wliile with the other there were also introduced iufusorial animalcules, the^latterwere

much

_stronger,

more

_active,

and

thro"e betterthan the former."

This appears ^tobe very strong evidenceⁱⁿ favor of the auimalcular dietof these crustaceans. Other _{evidence, too,} of quite asconvincing a character isnot wanting. Those

who

have been in the habitof col- lecting (piautities of microscopic material from ponds

and

ditcheshave frequently observed_very large schools of Entomostracain such_places where the water as a rule is not absolutely stagnant, but where an abundance of duck-weed, fresh-water _{alg;© of}

many

kinds, as well as various water _plantsof the higher orders

make

a splendid nidus ^for

allkindsof

monads and

ciliated

and

amoeboid Protozoa. Thesearethe Xilaces where _Cyclops,Daphnia,

and

alliesflourish inlandin fresh water.

The

writer has also noticed

them

particularly abundant in the wide riverflats near the

mouth

ofthe Susquehanna ^at

Havre

de_Grace,where there are large areas

many

^{acres in extentwhich are coveredwith a}

liixuriautgrowth ^of Potamogeton^ Anacliaris.

and

Vallisneria,

making

^a d«use

mat

of delicate stems and leaves

upon

^{which countless multi-} tudesofProtozoa

may

^{fixthemselvesand abide. If,in} rowing through such massesofaquatic vegetation, one will stop the boatand stircare- fully

among

the plauts with the

hand

over the side

and

_cautiously

w^atch the _result, one willoften notice that great n^^mbers ^of Entomo- stracahave been _frightened from their leafy ^retreats. These are the places where

young

shad ought ^to be liberated; ⁱⁿ such _idaces they would find anabundanceof food at an early period, or assoon as they werefitted to partake^ofnutriment

by

swallowing.

Just as

we

find the freshwater formsof Entomostraca take to the shelter ofaquaticvegetation ^atthe

mouths

of _rivers, soitappears that

many

^{of the marine forms seek} i)rotection, and probably food,under cover of the frondsof marine algtie.

Here

is

what

their most recent

monographer

saysin relation to thispoint^: '^A large

number

of species haunt almostexclusivelytheforestsofX^minfflr/fcwhich

grow

on rocky coasts at

and

belowlow-water

mark;

^{the frondsof}

Laminar

iasaccharina in particuUir arethe favorite abodeof

many

species." (Brady,Monog.,

Brit. Copep., ^Introd. I, p. 7.) Again, on page 9, he _remarks,

"The

washing^{of the fronds} and roots of Laminarirc, which

may

be dragged

up by means

^{of the hooked} grapnels used on

many

^coasts

by

kelp- burners, often affordsmultitudes ofCopepoda."

They

appearⁱⁿ

many

^{cases to be surface swimmers. I}have myself seen schools of several thousands of

Daphniadw

^of a greenish yellow color inthe ditchessouth of

Camden,

^N.J.,

swimming

^{at the surface of} the water at

midday

ⁱⁿ the bright sunlight. In the vicinity of

Wood-

bury, ⁱⁿ the

same

_State,

my

friend, Mr.

W.

P. _Seal, has taken great

numbers

ofabright red-colored Coi>epod,apparently^relatedtothegenus Pontella,

and

j>erhaiis undescribed.

They

^were sufficiently abuudant in

some

cases to imparta red tinge^to the water.

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

239 Brady (Mouograph

^British Copepoda) ^{observes in liis} introductiou, vol. _i, page^9:

"The

beds offresh-water lakes

seem

tobe verysparsely populated with Copei)oda,

aud

as to

swimmiug

species ^it may, ^as a general rule, be said that the weedier the pool

and

the smallerits ex- tent,themore abundantin all])robabilitytheEntomostraca.

"

Many

^{of the marine} species pass ^theirlifeapparently near ^thesur- faceof theopen sea,

and some

_{of these,} such as Calanus finmarchianusy Gunner,

aud

Aiiomolocera Patersonii,Templeton, ^are frequently found in

immense

_profusion, the first-named_species having been ^{said to}form a very important part^ofthe foodof the Greenland _whale,

and

itisre-

markable thatin the Arcticseas not onlydo the Entomostraca attain an enormous development ⁱⁿ point ^of numbers, ^{but alsoin individual}

size; Arctic specimens, ^forexample, ^of Calanusfiinmarcliianus

aud

Me- iridiaarmata _being

many

^{timesthebulk ofthosetakeninour}

own

lati- tude." _{I.e.)

According^toH.

Woodward,

^{in his article} Crustacea, Encyclopaedia Britannica,the fecuudity^ofthe

Copepoda

^istruly surprising. "

Cyclops quadricornis^is oftenfound with thirty or forty eggs on each side,

and

though^those species which have but a _single ovisac do _{not carry} so many, ^their

number

is still veryconsiderable. Jurine isolated _speci-

mens

of Cyclops,

aud

found

them

_{to lay eight}or ten times within three months, ^{each time} about_fortyeggs.

At

the

end

of a yearonefemale

would

have produced 4,442,189,120

young

^{! Cetochilusisso}abundant, both inthe northernseas

and

in the SouthAtlantic, so as to servefor food to such an

immense

animal as the whale.

They

^{color the seafor}

many

^{miles in}extent,

and when

the experiencedwhaler sees thisruddy, hue

upon

^{the ocean he}

knows

he has arrivedatthe 'pasture^of the whales'.

They

^{are to be seenin vast} quantities^oft" the Isle of

May

ⁱⁿ

theFirth ofForth during^the

summer

months.

Many

^{Cetacea are at-}

tracted_thither,

and

vast shoalsof fish also

come

to feed

upon

^them.

One

anomalous _typeof free copepod ^is the ISotodelphys ascidicola, de- scribedby Allman, which ^is found

swimming

freely in the branchial sackofAscidia communis.''''

The

_writer, in passing,

would remark

that he has_frequently

met

with

Copepoda swimming

freely in the ventral part of the branchial space

ofil/j/ftarenaria, ⁱⁿwhich the animalswere probably^notparasitical or

commensal, but

had

been

drawn

fromwithoutintotherespiratoryspace of the molluskthroughthe incurrent part^ofits siphon.

In the

same

articleas previously quoted

Woodward

observes:

"The

Cladocera are _chiefly fresh water,

and

are distributed overthe whole world.

Of

this order the Daphnia pulex, so abundant in our

[British]

fresh waters,^isa good example. So

numerous

are theyⁱⁿour_{jjonds in}

summer

asfrequently^to impart a blood-red hue to the water for

many

yards ^{inextent. In order to realize}the wonderful fecundity^ofthis

and

allied genera,^{it is}necessary ^torealize that

when

a

Daphnia

^isonly ^ten days^old eggs

commence

to be formed within thecarapace,

and

under

240 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

favorableconditious of light

and

temperature^it

may

^{harethreebroods}

a month, ^or even_{a greater}number,^thelarger specieshaving^as

many

^as

forty or fiftyeggs ^{at once."}

The

remarkable_fecundityof the

Copepoda

explains theextraordinary

abundance

of the free-swimming species

upon

the high seas,

and

even bays,

where

vast schools of thesecrustaceans become, ⁱⁿturn,thefood ofvast schools of herrings,

menhaden, and

^shad. Doubtless, themove-

ments

ofthese fisheson _{the high} seasaredetermined

by

^{the abundance}

of their favorite food in various localities; that, like the whale, they seek theirmarine _pastureof crustaceans, as argued

by

^Mobins.

Even

largerformsof_fishes, suchas the

huge

basking shark {Cetiorhhmsmax- imus), has its branchial apparatus adapted ^to capture small jielagic organisms, ⁱⁿthe

same way

^as the Clupeoids.

The

jirodigious

numbers

of herrings

and menhaden

is a _jiroof of the abundanceof the minute pelagic organisms

upon

which, with scarcelya doubt, ^it

may

^be sup- posedthey ^{subsist. It is also} not improbable^{thatthevast schools of} pelagic Entomostracans are in pursuit^{of still} smaller protozoanprey,

upon

^which they ^{subsist aiul} maintain their marvellous reprodu<;tive powers. Moseley,^inhis "Notes

by

^aNaturalist on the Challenger,"^ob- serves:

"The

deadpelagic animals

must

fall asa constant rainof food

upon

the habitation of theirdeep-seadependents. Maury, speaking^of the surface Foraminifera, wrote, 'The_{sea, like} the snow-cloud, with^its flakes ina calm, ^is always letting ^fall

upon

^its bed showersof micro- scopic shells.'" Moseleyrecords that he_estimated, from experimental data, thatit would take fourdays and ^four hours for a dead _Snliya to fall to thebottomwhere the sea

was

2,()()()fathoms in depth.

The

_deep- seafauna isprobably well supi)lied with food from such sources.

The

researches of Mr.

John Murray

^of the Challenger fully confirm

and

greatly

expand

^the significance of the views of lieutenant

Maury

ⁱⁿ

relation to the destiny ^of the marine foraminiferpJ shells. Wyville

Thompson, Voyage

^of the Challenger, I, 210, observes: "Mr.

Murray

has combined with a careful examinationof the soundings ^{a constant} useofthe_tow-net, usually^atthe_surface,butalso atdepths from ten^toa thousand fathoms; and he finds the closest relation to existbetween the surface tauna of any particular locality

and

the deposit which is

taking place ^atthe bottom. In allseas,from the equator ^to the polar

ice, thetow-net contains GlobujerinceJ^

Some

of these surface Forami- niferaare _{relativelylarge,} Orhnlina universabeing^as

much

asafiftieth of aninch in diameter, and hence of a sufficient sizetobe preyed

upon by

^alargerarthropod.

The

remarkable_PyrocystisnocUluca, discoA^ered

by

^Mr. Murray,

and

nearly a millimeter ⁱⁿ diameter, ^is another inter- esting surface form, ^{as is also} the P.fusiformh^which is allied to it.

Both

are phosphorescent^surfaceswimmers, and ^{fall within thereachof} other surface animals as a probable source^{of food.}

To

these

may

^be

added

the curious group ^{of the} Challengerida, together with the whole of theBadiolariaj^"sviththeirsiliceous shells,which,ⁱⁿ the

warmer

_parts

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

241

of the liigb seas, actuallytinge the ^surface

when some

of the _highly- coloredformsareabundant.

From

the surfaceof the mid- Atlantic the Challenger crewobtained stalked infusorians fixed tothe shellof _Spi- rula, also an abundance of largeradiolarians. Haeckel,

Monograph

^of the Eadiolaria, says the largest living Eadiolaria measure _{only a} few

lines in diameter, but most of

them

are

much

_smaller,

and

attain scarcely a tenth,

down

toa twentieth of a line in diameter.

At

Saint Jerome's Creek, Maryland, ⁱⁿ an

arm

of the _former,

now

used as

an

oyster park, the writerfoundan abundance of afresh-water_Heliozoan, notspecificallydistinguishablefromActinophrys^sol.

They

^{were found}

ingreat abundanceat times on the surface ofthe slate collectorswhich

had

_{been put}

down

for the purpose^of enabling thefree-swimming ^fry ofthe oyster ^{to fix itself.} This raises the question whetherthe fresh- water _protozoan fauna does not overlap the marine.

The

waterinthe situationmentioned

was

notsimplybrackish,but_positively salt. In the

same

place great

numbers

of stalked

and

tube- ortest-building^ciliate formsof Protozoawerealsofound.

The

magnificentbottle-greenFreia producta

was

foundinthe

same

_localityinthegreatest profusion. Some- timesseveral

hundred

might have been counted^{on a}singlesquare inch^of thesurface ofoyster shells,slates,orboards, givingsuchsurfacesa dark- greenish ^or speckled ^tint from their numbers.

Very

^small species of nudibranchiate mollusks {EoUs

and

_Doris)were foundcreeping amongst andover the forestof Protozoa, i)asturLng^off of them.

Amongst

^the

tubes of the_Freia,and attached tothem, a small operculate Cothurnia, with arich brown-colored _test,

was

found in abundance, and, rarely, a very curious form of Tititinnus, with a _tubular, subulate _test, to the inside of which the stalk of the inhabitant

was

_attached, at one _side, abouthalf

way up

^fromitsbase.

The

_open, ^or_{mouth, end} of the _per- fectly hyaline^test

was

_very strongly toothed, ^{or serrate.}

The

species

may

^be

^named

^TintinnusFergusonii.

Another

_{species of}Freiahas been detected, on the coastof

New

_Jersey,

_by

Professor Leidy, and,from a verbaldescription given

me _by

Dr. H. C. Evarts, aspeciesoccurs inthe

'

vicinity of Beaufort, N. ^C. So abundant

was

Freia producta ⁱⁿ Saint Jerome'sCreek thatI apprehend^{thatin its} free-swimming

young

state, previous^tothe time thatit

commenced

to builditstest, ^it affordednot an inconsiderable proportion ^of food to the _oysters planted ⁱⁿ

some

parts ofthosewaters. Besides theFreia there were innumerableindi- viduals of Vorticellaobserved.

One

of these

had

avery thick, brown- ishcuticle_; butfor

numbers

th<^sewere _againverygreatly exceeded

by

the

compound

^stalked genera of bell-animalcules.

Upon

the very com-

mon

_alga,Laminaria, these were abundant,

and upon

^{the fronds of} another _alga, the Grinnellia,ⁱⁿ threeor fourfathomsofwater, near the middle of the Chesapeake, ^their

number was

truly astounding. In a few such _places wherethese _algsewere dredged

up

^from the bottom, covered withinnumerable coloniesof protozoans, ^itwould doubtlessbe

much

withinbounds to statethat there were1,000 individual protozoan

Bull. U. S. F.

C,

^{81 IG} Api-ii

S§,

¹

⁸ 82,

242 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

zooids to the superficial square ^{iucli of} frond surface.

At

this rate therewould be39,204,000 zooids foundtopopulate a single square rod of frond surface. Estimating ^the

number

at only 100 persquareinch, whichislow,

and

which _would, I think,represent a ^fair average over considerable areas where the conditions of life were favorable, there

would

stillbea stalked protozoan population^of nearlyfour millions to the square ^rod.

The

most abundantof these

compound

^forms

was

one which _very

much

resembles Zoothamnium_{alternans,Glaperede,}foundon the west coast of Norway.

The same

form was_again found in vast abundance

upon

algsB in Cherrystone Eiver, near the

mouth

of the Chesapeake, during ^{theseason of 1881.}

Upon

^{oneoccasionIfound it}

in great abundance growing on ^all parts ^of the

body

^{of a}Finnotlieres which

was

_{living in} thegill-cavity ofan_oyster, itsswarmers, ^oryoung, asthey were thrownoff, inallprobability formingpart^ofthefood _sup- ply^of themollusk.

Ihave beeninterested

upon

^{severaloccasionsto}observe that the very minutestalkedcollaredmonads,Salpingceca

Rud

Oodos_w/a,arefrequently tobe found attached tothe stemsof the

compound

^{colonies of bell-ani-} malcules,^or gathered about ^inthe vicinity of the point^of attachment of asingle one. In such cases the

monads

_appeartoderive abenefit fromthe currents or vortices set _uj) inthewater

by

^the

waving

^{of the}

ciliarycrowns of their giant neighbors, which_bring particles of foodto theirvery^{doors as itwere.}

On

oneoccasion I found individuals ofa species of ^Vorticella fixed tothe

egg-membrane

^{of the ovaof thecod-}

fish at

Wood's

_Holl,Massachusetts,^as

had

been_previouslyobserved

by

E. E. _Earll,

and

in their vicinitywere several colonies of a

compound

stalked monad,resembling the Dinohryon^of Ehrenberg.

On

another occasion I found something ^like Poteriodendron on the Zoothamnium which covered a Pinnotheres inhabitingan _oyster; but the chain _{of par-} asitismdid not stophere, foronthemonad,^{aswell as}onthe bell-animal, there were rod-likebodies attachedwhich were presumablybacteroid, ashas been supposed

by

^{Stein. Stalked}

monads

are probably

much more common

than has been _supi)osed, which reminds

me

thatI have detected the occurrenceof PMpidodendron splendidmn ⁱⁿ the bogs

and

ponds ^of

New

Jersey, a form which

was

described _originally

by

^Stein from Bohemia. Minute as the stalked

monads

_{are, they}

must

Uve on

still minuter _beings,probably

upon

the Microbia, which in theirturn

become

an indirectsourceof supply^{of foodfor}the grades nextabove them, such^asthefree

and

fixedciliateProtozoa,whichfeed

upon monads

which have themselves fedon Bacteriaor Bacillus-likeorganisms,

and

so

onward

the matterof life takes its

upward

way.

The

_process of swallowing ^of

many

^ciliateinfusorians is as peculiar asit isinteresting.

An

_opening, oftenest atoneside ofthe body, ^isthe mouth, from which ^ashort blind canal passes^{into thesoft}substance of theanimal's body.

The

_rapid vibrationof rowsof ciliain the_vicinity ofthe

mouth

createscurrentswhichset in inthedirection of the throat,

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

243

the lowerend ^{of whicliis dilated into a} globular space

by

^theforceof the currents produced

by

^{the cilia, in wliich the i^articles of food are}

rotating-in the contained water. This space enlarges gradually^until eventually ^its connection with the throat is suddenly broken

by

^acol-

lapse of thewallswhich _jointhe globular space with the ^former. In

this

way

food-vesicle after food-vesicle is taken into the

body

^{of the}

animalcule,from whichthe creaturewillabstractwhateverisuseful

and

cast out near the

mouth

whateveris contained in the food-vesiclesthat

is indigestible.

The

writerhas seen the process ⁱⁿ a

number

_{of forms,} and ^{it is not} unusual to observe adozen or

more

food-vesicles in the

body

^ofasingleprotozoan.

Many

parasiticforms, however, ^are*mouth-

less,such as Opalina,Benedenia, Pyrsonympliaj Trichonym2)ha,&c.,where the nourishment^isprobably ^obtainedfrom their hosts

by

transudation through the body-walls. In other forms _again comparatively large objects are swallowedwith apparentease, judging from^{shells of other} protozoan tyi^es which are found within their bodies.

Such

aformI encounteredin a_slightlybrackish water-pool near

New

Point Comfort, Virginia, during ^the

summer

of 1880. It

was

apparently a very large species of Prorodon of an irregular cylindrical form which had in a

number

ofinstances swallowed fiveor six largedifflugians, Arcella vul- garis,the shells of which remained within the animal to _testify tothe natureof the food it

had

been _devouring.

Some

other

mode

of swal- lowing such largeprey^isprobably practiced

by

^this largeciliate, very differentfromthe

method

firstdescribed. In the

same

_{pool averype-}

culiarformof hyi)Otrichous iufusorian

was

_detected, which

was

_clearly very nearly^{allied to} Chilodoncuctdlulus of Elirenberg, but the _dorsal, non-ciliated side of its

body was

not gently rounded, but flatwith a prominent^crenaterim surrounding ^it-, from this peculiarity^it

may

^be

called Chilodon coronafvs.

The mode

of swallowing ^theirfood adopted

by

the fresh-waterrhizo- pods ^has been elaborately described ⁱⁿ a fewinstances

by

^Professor Leidy^inhis splendid

monograph

^{of this}grouj), published

by

^theGeo-

logical Survey^ofthe Territories. Their foodappears^to be mainlyveg- etable,

and

consists, forthe

most

_{part, of}diatoms

and

_{desmids, though} a ciliated protozoan ^orrhizopod

was

occasionally

met

within the

body

ofAviKha.

The

marine_rhizopods appear ^to be herbivorous as well as carnivorous,remainsofboth Protophytes

and

Protozoa having been ^de- tectedin theirbodies. Vampyrella has been described as almost_para-

siticupon^the clustered frustules of Gomplionema.

Some

aberrant ciliated forms, ^like the Gastrotricha

and

_Coleps, are

somewhat

peculiar in their organization,

and we know

little of their feeding^habits.

The

Suctoria or Tentaculifera, which are abundant in

some

_places, bothin freshand saltwater, appear^{to be} indiscriminatelyherbivorous, as well as carnivorous. In fresh water ^I have

met

with

them

_infesting thebackof the

common

water_{leech, Clepsine^}the species being appar-

r

244 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

ently Podophrya quadripartita.

Of

marine _forms, ^I have seenbut two thatI could regardas distinctfromeach_other; the _one,a vQry

common

form,^istheold

and

well-knownAcineta tuberosaofEhrenberg,^with two clusters of suckers. This form I have frequently seen with diatoms whichit

had

seized

and

fromwhichit

was

abstracting nutriment.

The

otherform

was much

_largerthanthe precedingand _appears to beiden- ticalwith the _species described under the

name

Podophrya gemmipara

by

Hertwig. ^Ithasthe

same

robust_stalk, with the

same

closetran.

verse annular markings, the

same

_taper,

and

is similar inthe form of the_tentacles, whichare often irregularlybeadedor swollen. I

was

en- abled 4o observein part ^itsdevelopment, which ^{isalsosimilar to that} oftheHelgoland speciesof theNorth Sea abovementioned.

They

^were foundin great abundance on thesurface of the fronds of Laminaria, together with the Acineta _tuberosa; not as abundantly, of course, as the Zodthamnium, ^{butin sufficient}

numbers

to

make them

_{a very} con- siderable factor inthe protozoan^lifefound inthe_vicinit}'of

New

Point Comfort.

The

_majority of the free j^rotozoa

and many

monads, such^{as Nocti-}

luea, have_scarcelybeenconsidered, but enough^hasbeen _{said, Ithink,} togive

some

ideaof the actual importance^{of the} minute animal

and

vegetable ^lifeof the sea to

make

itclear that thereis amostintimate relation of dependence existingbetween the lowest

and

the inteniio- diate forms of life.

Why

^is it, for example, ^that

we

should find the

Copepoda

^soabundant

among

^the

^Laminar

^iaalong the^sea-coast?

Have we

not

shown

that on the fronds of these _algae there _exists, in most instances, almost aforest of protozoan life,

upon

^whichthese creatures

may

be supposed ^to pasture"?

We

^{do not find the} Laminaria itself eaten. Again, ^theforaminiferal

and

radiolarianfaunaof thehigh^seas appearsto be, in great measure, a surface fauna, according ^totheevi-

denceof a

number

of investigators. This fact appears ^tohave an im- portantrelation tothe vast shoals ofCope])oda observed ^atthe surface of the sea

by

^various naturalists and expeditions. ^Itis notto be_sup- posed, however, from

what

has been _said, that the

Copepoda

^{are the} only consumers of this vast array of individual protozoa. Cross-sec- tionsthrough^theoyster, which the writer has prepared

and

_mounted,

show

the tests of various genera

and

_sx)ecies of diatoms

mixed among

theindigestible earthy mattersand sediment which has been swallowed along with the^{food. Itis}i^robablethatthe_oysterswallows

and

_digests

many

^{of its}

own

_embryos,

and

not improbably

many

embryos ^of such formsasBryozoa

and

_sponges,besides the diatoms, desmids,

and

_proto- zoawhich

make _up

the

most

of its food. Ordinarily the contents ^of the stomach of the oyster are too

much

disorganized ^{to learn}

much

about

what

it has _{recentlyswallowed,}hence

we

are at a great ^{loss to}

know

_{just exactly} of

what

all ofits food consists; just so with the

Copepoda —

they themselves ^are doubtless eaten

by

other Crustacea, thesein turn

by

^others.

We saw

that Doris and Eolis jDastured

upon

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

245

the forests of fixed protozoa, just as Planorbis,Lymnaeus,

and

_Physa pasture

upon

the protozoa, algse, diatoms,

and

_desmids, infresh water.

The

_great ^abundanceof

Copcpoda and Amphipoda

is,however,^{the best} evidence ^of the abundance of still smaller forms adapted ^{to furnish}

them

with food.

What

multitudes of forms besides

Copepoda must

largely subsist

upon

the protozoa

and

protophytes.

Of

such groups

we may name

the Lamellibranchs, Pteropods,

Worms,

Bryozoa,^Porifera, and,doubtless,

many

Coelenterata.

Some

_{of these,}notably theLamel- libranchs, couldprobably ^{not exist}were it notfor the

numerous

_proto- zoa

and

j)rotophytes,

upon

which,from_necessity,they are comiielled to feed.

What

istrue ofthefaunaofthe sea appears^tobeinan _equallygreat measure true of the faunae of fresh-water ponds, lakes,

and

streams.

Eecently ^Iinvestigated

some

Daplmiadce which

had

_{been kept} for

some

timein an aquarium; ^to

my

surprise ^I did notfind

any

recognizable ^re- mainsofanimalfoodintheintestine.

The

latterwere,however,^entirely

filledwith a sarcode-like material, doubtless in _jiarta _digestive secre- tion,together ^with,

what

_{might have}in_ijart been animal food.

The

vegetable food,consisting^of diatoms,unicellular _algte, spores of fungi, fragments of oscillatorise, were so sparingly

mixed

with the intestinal contents that they could notbe regarded ^as contributing

much

to the nutrition ofthe animal.

The

black or

brown

_material,sometimesfilling theintestine of Entomostraca, I find to consist in great part^of

humus,

particles of quartz sand

and

earthy matters,

which

are of course indi- gestible, beingthrown out of the _{vent, as} in Chirocephali, ⁱⁿ theform of cylindrical^casts.

The

mostvaluable contribution to ourknowledge ^{of the food ofthe} fresh-waterfishes of thewestern UnitedStates has been

made _by

Pro- fessorS.A._Forbes,inBulletinsXos. 2

and

3oftheIllinois StateLabora- tory of ^ISTatural History, ^forthe years 1878

and

1880.

With

themost painstaking ^care theresultsof a vast

number

of examinations are re- corded.

He

finds that the Darters, Perches,Lahracidce, Centrarchoids orsun-fishes, Scisenoids, Pike,

Bony

Gars, Olupeoids, C^'prinoids,Suck-

ers,Cat-fishes,

and

_{Amia, both} the

young and

adults,

consume

_large numbers of small_aquatic,

and

occasionallj'' smallterrestrial organisms, notably the smaller Arthropods.

While many

^{of the}

^more

^voracious

species, both

young and

adult,feedontheirimmediate_allies,the dietary of the fishes of _Illinois, according ^tothis observer, includes mollusks, worms,fresh-water Polyzoa, Hydrachnidse, ^{insects of} both mature and larval forms; Crustacea, embracing Decapods, Tetradecapods,

Amphi-

pods, Isopods,

and

Entomostraca of the groups Cladocera, Copepoda,

and

_{Ostracoda; Eotifera,}Protozoa, vegetable matter,

and

_algse. In his firstpaper healso gives a hstof theorganisms found^inthestomachs

and

intestines of the Pirate_perches, Gasterosteidci',Atherinidm^ Cyprin- odontidce, Umbridce, Hyodontidcv,

and

Folyodontidce.

Both

are accom- panied by ^elaborate comparative tables, and,ⁱⁿ an economical _sense,

246 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

are of tlie greatest practical importance ^{in tlieir} bearing

upon

^fisli

culture.

It has, however, been

known

_longagothatfishes

consume

_largequan-

tities of small Crustacea, as ^willbeseen fromthe following ^extractfrom Dr. Baird'swork:

"Thatthe Entomostraca forma considerable portion ^of the food of fisheshas_longbeen _observed,

and

itisveryprobable that the _quality of

some

ofour fresh-water fishes

may

ⁱⁿ

^some

degree

depend upon

^the abundanceof this portionof their food. Dr. Parnell informs

me

that theLochlevintroutowesits superior sweetness

and

richnessof taste to its food, which consists of

smaU

shells

and

Entomostraca.

The

color of the Lochlevin_trout, he fartherinformed_me,isredderthan the com-

mon

trout of otherlocalities.

When

_specimens of this fish have been

removed

fromthe loch

and

_conveyedtolakesin other_places, the color remains, but they very soon^losethatpeculiar delicacy of flavor which distinguishes soremarkably^{thetrout ofLochlevin.}

The

_experimenthas been _repeatedlytried

and

always with^the

same

results.

The

baustickle [Gastrosteus trachurus] devours

them

with _{great rapidity,}

and

I have seentwo orthreeindividuals clear in asinglenight alargebasinswarm- ingwith Daphnise

and

_Cyclops, &c."

The

writer

would

also refer toarticlesonthefoodoffishesintlieEeports oftheUnited StatesFish Commissionerfor1872

and

1873

by

^Professors Milner

and

_Smith,

and

topapers

by Widegren and Ljungman

^{on the} copepodan^foodof herring. Alsoapaper

by

^{Dr.C. 0.}

Abbot

inthe

same

report, ^for1875 and_1876, onthe winter habits of thefishes oftheDel- aware.

Mobius

has found i^eces of algse, besides shells, snails,crabs, andfishesinthestomachofthecod.

The

writerhasfoundthestomachof the sheep's-head^filledwith the remainsoftheshellsofmussels

and

_large

quantities ofthe slenderbranchesofthe

common

_{bright red}S])onge,Micro- cionaproliferiim, bitten ^off in shortfragments

by

^the incisor-like teeth of the _fish,

and

withthe red sponge ^sarcodepartlydigested out ^{of its} skeleton. Itis

presumed

^{that the} sponge ^feeds

upon

protozoan life,

and

on account of its peculiar dentary armature ^the sheep's-head ^is singularly well ^fitted to pasture

upon

sponges

aud

thus _{indirectlyap-} propriate protozoa ^as nourishment.

The same remark

applies to the molluscanfood of thisfish.

In

young

^{shad from}Capehart'sfishery,Albemarle Sound,^saidtohave beenthree weeks_{old, I}foundtheremainsof a

number

of adult _Tipuli-

(ke, orcrane-flies,in theintestine. Thisreminds

me

that inexamining thelarvae ofcrane-flies

some

_yearsago,I

was

struck with thefine comb-

likefringes which garnish the edges^{of their} wideoralappendages,

and

whichare soextendedinlife

when

the larvaisinmotion as to constitute a sort of basket which opens

downwards and

forwards apparently ^to strainout ofthe waterthe small organisms which ^{constitute its food.}

Here

_again

we

have

young

^shad feeding upon an arthropod which has passed^itslarval existeuce, feedingⁱⁿ great part

upon

protozoa. West-

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

247

wood, Introd., 11,511, ^I find,

makes

asimilar observationinregard^to thelarva? ofthegnat^or mosquito famJly.

He

_says:

"The

headisdis- tinct, rounded,

and

furnished withtwo inarticnlated antennte,

and

sev- eral ciliated appendages, which ^serve

them

for obtaining nourishment from their food."

The

fixed Tunicates are probably ^as dependent

upon

the microscopic

life

swimming

^about

them

in the water as the Lamellibranchs.

The

Barnaclesin likemanner,

immovably

^fixedduring^theiradult_existence, kick their minute food into their

mouths

with their filiform legs, as remarked

by

Huxley. ^In Pedicellina aniencana, abundant in Saint Jerome's Creek, ^Ihave observed that there are rows of vibratory ^cilia continuous with those of thetentacles around the edge ^{of the} lopho- phore,which appear^{to liein} grooves, which blend oneither side of the excentricallyplaced mouth. In this

manner

the microscopic food ^of this curious bryozoan ^is conveyed ^{in ciliated} grooves ^to the

mouth

from allpointsof theoral disk.

With

these

we may

^closeoursurvey of the

modes

in which the _i)rotozoan grade ^{of life is} ai)propriated the smaller Arthropods, Pteropods, Polyzoa, Annelids,

and

_Tunicates, but

we must remember

that

upon

^these again the _larger loims subsist, which are either food for each other or for man.

As we

pass ⁱⁿ succession the _{larger forms,}

we may

note the Lamellibran- chiates, with this garniture ^of vibratory ^cilia covering the gills

and

palps,

and

which _{carry the} particles of food

and

sediment suspended in the water used ⁱⁿ respiration to the

mouth

to beswallowed.

The

Clupeoids

and

Cetiorhinus withtheir branchical sievesare particularly noteworthy^{for the} perfection of the apparatus ^of prehension,but

we must

not_forgetthatthe gill-rakers of^allfishes,

whenever

_developedto

any

extent, probably ^{subserve a similar function.} Lastly, the _right- whales, with ^their closelyranged plates of baleen suspended from ^the upperjaws, forming ⁱⁿ reality a

huge

^{strainer or filter for the} large volumesof sea-waterwhich _pass through ^the mouth,

and

from which thefood of thesemarine _giants is sosimply _obtained, ^{willenable us in} ameasureto

comprehend

^theimportance^ofthe minutelifeofthe world, anditsindirect but important^economicalrelation to man. ^.

THE FOOD OF THE YOUNG

SHAD.

The_{periods of} yeUc-ahsorption.

In a previous paper

by

^{the writeron} the retardationofthe _develoji-

ment

ofthe shad,^it

was

stated that the yelk-sack disappearedon the fourthtothefifth

day

^afterthe

young

^fish

had

leftthe_egg.

Although

this statement is in abroad sense_{true, I} find

upon more

^accuratein-

vestigation thatthereisa small

amount

ofyelk retainedⁱⁿ the yelk-sack for a

much

_longer time. It appears^{in factthat there} are really

two

periods^ofabsorption^ofthe yelkwhich

may

be verysharply distinguished fromeach other.

The

firstextendsfromthe timeofhatching^{to the}end

248 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

ofthe fourth orfifth day, according ^to temperature, duringwhichtime the mostof the yelk ^isabsorbed.

The

small quantitywhich remains afterthistimeisnotvisibleexternally,being containedⁱⁿa smallfusiform sack, ^all thatremains of the trueyelk-sack^inclosed

by

^{the abdominal}

walls,

and

causes littleornovisibleprominence on^theunderside ofthe

young

^fish.

Viewed

asa_livingtransparentobjectfromthe _side,

we

see itinthe

young

^fishlyingbelowthe oesophageal portion^ofthe alimentary canal immediately^{in frontof the} veryelongate liver,

and

behind the .benrt,with the venous sinus of whichit appears ^tocommunicate

by

^a

narroAvductformedof theanteriorportion^ofthe yelk hyboblast, which formerly covered the distendedyelk-sack.

The

appearancespresented

by

^the living transparent objects are _fullyconfirmed

by

the evidence obtained fromtransverse sectionsof embryos from^{ten to twelve}days

old. It appears that the yelk-sack of the^Californiasalmon probably behaves ina

somewhat

similar

manner

as indicated

by

^{transverse sec-}

tions. I evenfind this slightrudimentofthe yelk-sackⁱⁿshad embryos fourteento sixteendays old, but this seems to be about_{the period} of its disapi^earance.

The

second _period of the absorption ^of the yelk thereforeextends inthe shadoverabouttwice thatofthe _first,orabout ten _days.

The

firstperiod extends^tothe time

when

the yelk-sack^isno longervisible externally, the second fromthe timetheremains of the yelk-sack become inclosed in the

abdomen

until its final

and

_complete

absorption.

The

functionof the yelk-sack during the ^first periodap- l)ears tobe to build up ^the structures of the growing embryo; during the second, not^so

much

to buildit uj)as tosustainitin vigorous health until itcancapture food^toswallow

and

_{digest, so} thatit

may

^nolonger be dependent

upon

^{thestore offoodinherited from its}parent.

The airpearanceof^{the teeth.}

Minuteconical teeth

make

their appearance on ^{the lower} jaws and in the

pharynx

^ofthe

young

^{shad aboutthe second or third}

day

^after hatching. Sections through ^the heads of embryos

show

that these teeth are derivedfromthe_oral,hypoblasticlining ofthe mouth. There are none on the upperjaw, there^{are four} arranged symmetricallyon the lower jaw, or rather, Meckel's_cartilage. Inthe_throat,inthevicin- ity ofthefifthandlastbranchial _arch,there are

two

rows of lower pha- ryngeal teeth, the firstof_six, threeon a_side, the lastof _four, two on a

side. These teethare ofthe

same

form andsize asthose on_{the jaws.}

The _{age at}whichitbegins^to talcefood.

Although iDeristaltic contractions of the walls of the intestine of

young

^shad

may

be observed soon after hatching, ^I have never ob- served foodin the alimentary canal ^until ten or twelve days ^afterthe

young

^fish

had

left the _Qgg.

At

about the beginning ^of the second

week

considerable

may

^{be seen in living specimens.}

^But

^{the intes-}

BULLETIN OF THE UNITED STATES

FISH COMMISSION.

249

tine is often not yet very densely packed ^{with food} even at this period.

At

the age ^{of three} weeks an abundance of food is found

in the _intestine, that portion which becomes the stomach

and

which extends from the _posterior extremity ^of the liver to near the vent beinggreatlydistended with aliment.

Upon

investigating the nature of this food material

we

learn thatit consists almost entirely of very small crustaceans, in reality for the most _part of the very youngest Bcqjhniadw and Lynceiflcv; only once did ^{I find}

what

I thought might be very small OstraGoda ^or Cypridw. In

some

instances the undevel- oped ^{larvai of}

Daphniw

^{were noticed. In a few cases} green cellules

were observed in theintestines of shad larvse resembling Protococcus, but asthismaterialappeared^to beaccidental,^{it is} probably^not anim- portant elementof shadfood. In the

young

^fishesthe dark,indigesti- bleremainsof the foodof the_Daplinicealwaysremained, together with the hard chitinous parts, as long-curved cylindrical casts which _pre- served theshape^{of the intestines of} the crustaceans. In one

young

shad, twenty-two days ^old from the time of impregnation, measuring 14millimeters in length, ^I estimated froma series of sections through thespecimen^thatit

must

have

consumed

over a

hundred

minute crus- taceans.

The

oldestspecimens ^of artificially reared shad which

came

into

my

hands were

some

that

had

been overlooked in

some

of the hatching apparatus ^atDr. Gapehart's fishery in North _Carolina, where_they re-

mainedforthreeweeks afterhatching. In that time they

had grown

to a length^of 23 millimeters, oralmost oneinch.

The

air-bladder

was more

_developed

and

the stomach

was more

_decidedly differentiated thanin

any

previous stage. Inthe intestinesof theseIfound, beside black, earthy,

and

_vegetableindigestiblematter, theremainsofthe chit- inous coverings ^of small larv^al Diptera,

and

the remains of a very small adult _crane-fly,besides EntomostracaalliedtoLyneeus. In these specimens the dorsal ^fin

had

the rays developed, the continuous

median

larval natatory^foldshaving

by

^this time disappeared.

The mode

in whichthe

young

^fish capture^theirEntomostracan prey

may

^{beguessed fromtheir oralarmature.}

^Most

^fishlarvosappear^to be provided withsmall, conical,

somewhat

_{backwardlyrecurved,} teethon the jaws. Rathke,in 1833, described the_peculiar

hooked

teeth onthe lower

jaw

^{of the larvEe of} the viviparous blenny,

and

Forbes has ob- servedminute teethon thelower

jaw

^{of the}

young

Coregonus ^{albus. I} havealso

met

withsimilar teethon the lower

jaw

^{of the larval} Span- ishmackerel.

THE FOOD OF THE ADULT

SHAD.

The mouth

of the adult shad, ^{as iswell} known,^is practically tooth- less,and inthethroatthere are nofunctionally active _teeth, as in the larvai, so that the_latter,in

reality, have a_relatively

much

better de- veloped dentarysystem thantheir parents.

The

_adult,moreover, prob-