On the nuclear cleavage-figures developed during the segmentation of the germinal disk of the egg of the salmon

335

similarlymarked,^thedorsal

and

analwith adarkblotch on each _eighth ortenthray, the pectoral sometimeswithone or

more

brownishbars.

Not

abundant inthe

Bay

^of

Panama;

^severalspecimens were taken, the _largestabout 10 inchesin length.

Indiana University,

^December2, 1881.

OIV

THE

IVUCL.EAR

Cr-EAVAGE-FIOITRES DEVEIiOPEO DURIIVO THE

SE«.nE

STATION OF THE

OERi^lINAI.

DISK OF THE EOO OF THE

SAIilMOIV.

By JOHN

A.

RYDER.

The

factthatverycomplex changes ^areundergone

by

^nuclei during the segmentation ^{of cells has} been

known

for only a comparatively short time, and,

we may

add, ourknowledge^hasbeen_greatlyincreased

by

^{the recentadvances}

made

in the perfection of histologicalmethods.

The

titlesof the _j)rincipalmemoirs onthe _subject are given below.*

From

the listof papers, ^itwill begathered that^allare

German, and by

only afew authors.

The

lirstofthem. ProfessorFlemming, has ^de- scribed

and

_figured such remarkable cleavage-figures, which he has claimedto have observed insegmenting cells, that it isnottobe won- deredat that

some

cotemporarieshave been inclined to beincredulous.

SinceIhave been _{enabled,however,} to observe

some

of these phenom- enafor myself, ^I

am

_{quite well} convinced thathe has given usresults, thevalueofwhich cannot perhapsjustyetbe _proi^erlyestimated.

I recentlyreceived a series of ova of the

common

_salmon,

some

of

them

in the second

day

^of development, from Mr.

H. H.

_Buck, of Or- land. Me., ⁱⁿwhichvery comi)lex

and

interestingnuclearchanges were in progress.

The

germinal disk

had

_{not yet}

begun

^tospread ^to form the blastoderm, butthe cleavage

had

advanced so farthatit

had

been segmented^intoseveral thousand _cells, each measuring about 3-5-0tli of aninch in diameter. These salmon ova

had

been i)reserved in

weak

alcohol, sothatthey were^notquite asgood, perhaps,^forourstudies as theywould have been

had

they been hardened ⁱⁿvery

weak

chromic

acid.

The

cellswere, however, veryclear, so that

any

^nuclear figures couldbewell seen even without other_reagents, though

upon

^immers-

*^W.Flemming. Beitrjige^ziirKentniss der Zelle unci ihrerLebenserscheiniiugen.

I Part,Arch. f.mikr. Anatomie, XVI; ^II Fart andsupplement, Ibidem, XVIII; ^III Part,Ibidem, XX.

W.'Flennning. UeberdasVerhalten desKerns beider Zelltheilung undUberdie Bedentimg mebrkerniger^Zelleu. Virchow's Archiv,LXXVII.

Peremescbko. Ueberdie Theilung tbierischer Zellen. Arch, ^f. mikr. Anatomie, XVII.

W.Pfitzner. Die Epidermisder Ami^hibien Morphol. Jabrb., VI.

W. Pfitzner. Ueber denfeinereuBanderbeider Zelltheilung auftretenden faden- formigeu Differencirungen des^Zellkerns. Morph.Jahrb., VII,^lift.2.

W.Pfitznex-. Beobacbtungen^{iiber weiteres}Vorkommen der Karyokinese. Arch.

f.mikr. Anatomie,XX,^Hft.1.

336 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

iug ^tlie disk for

some

time in acid carmine, the ^nuclei were _verydis- tinctlybrought out, so that all the phases ^of change which they un- dergo ^could be observedin different individualcellscomposing ^thedisk.

In

some

cellsthe nucleiwere inthe resting stage; ⁱⁿfact, such

was

the casewith the_majority,and a comparatively small

number

wereobserved tobe undergoingcleavagewiththe nuclearmatter aggregated^atoppo- site endsofthe

now

elongating nuclearfigure.

Every

r>hase ofnuclear metamorphosis^could be studied deliberately after ^I

had made

_perma-

nentbalsam preparations,

and

fromtheseIhave been enabled to

make

a

number

of camera _sketches, which are almost as complex ^as

any

figured

by

Flemming. These sketchesareappended ⁱⁿan accompany- ingplate.

Itisnot

known

in

what

respect the nucleus ^differs chemicallyfrom therest ofthe protoplasm ^{of thecellin} which itis embedded, ^{but itis}

known

thatitisin

some way

very intimately concernedⁱⁿ the process of cell-division, a

phenomenon

which always accompanies growth

and

development. In the case of almost all,perhaps^all orgaoisms, the^cells which compose

them

areconstituted ofacentral

more

orlessrefringent body, the nucleus involvedⁱⁿ a covering^ofprotoplasmusually

more

or less different in optical properties from that composing ^{the former.}

Huxley

observes (Anat.^Invert. 19),

"when

nucleated cells divide, the divisionof the nucleus, asa_rule,precedes that^ofthewhole cell." This appears^to bethe fact inthe case of thesegmentation^ofthecellsofthe germinal disk^of the egg^of the salmon, but_just

what

sbare theenvel- oping protoplasm

may

^takein the process

we

do not _certainly

know;

doubtless the enveloping protoplasm ^isjust as necessary^asan aid or accessoryⁱⁿ the process^asthenucleus_itself; they^areprobablyⁱⁿ

some way

complementary ^{to eachother.}

To

support ^thisview

we

have the additional factthat

we know

_nothingofabsolutely

naked

_nuclei, noris

theevidencein favorofabsolutely non-nucleated^cells

much

more than negative.

The

constancy withwhich complexcleavage-figures have re- cently been observed in plants, Infusoria, Protoplasta, 3IoUusca, Echi- nodermata, Arthropoda,

and

Vertehrata, both in the adult and

embryo

condition, would argue ^that theyinvariably

accompany

^{andcharacter-}

izecellular fissionorsegmentation, and,inasmuchasthe_rei)utedlynon- nuclcated

Monera

_propagate

by

fission,pass through a resting stage just^likethe cellsofother organisms, ^it would notbe_surprisingtofind that they^too were provided ^{with nuclei}whichwould_{developcleavage-} figures in the actof fission. Their complete parity of behavior inall

other_respects leadsustolookforimportantrevelationsrespecting^their complete morphological corresi)ondence with other types^{ofcells as}soon as they^arestudied

by

the help ^ofimproved methods.

Having

given thepreceding sketch^ofthefunctionandcharacteristics ofnucleithroughout^{the animal}kingdom,

we

areprepared^{to deal}some-

what more

intelligently with the _special case of the cleavage- figures which

we

have observed in the ova of the salmon.

The

_changes ^ob-

337

served iu thecellsofSalmo salaragree^{in all}essential particularswith those seen

by Flemming

^{in the cells of the skin}

and

branchire of the Salamanderof Europe,

and

are of interest as confirming ^his observa- tions and also as showing clearly^forthe first time that similarphe-

nomena

^occuriuthesegmenting^cellsofaspecies of^fishwhich has been perhaps morethoroughly studied embryologicallythan any ^other.

Fig. ¹represents a^{cell of}the germinal disk^ofSalmowith itsnucleus in the quiescentor resting stage magnified about 800 _times, which is

the amplification ofmost of the_figures. Inthis condition the nucleus

isapproximately globular

and

traversed

by

^averyirregular

and

inter- rupted network of aggregations,consisting of broken thread-like

and

rounded_granularbodies. This condition isthe one which

may

^besup- posed ^{to exist}duringthe long ^{intervals of rest} between the periods of active segmentationwhich have been observed

by

different biologists during the veryearlystages^ofdevelopment^oftheovaofvarious _types.

This intervalof rest

may

^alsoinclude a portion^ofthe stages ^of change undergone

by

the nucleus preparatory^to cleavage,

and

whichwill be next described.

Fig. 2represents the nucleus of a ^cell from the

germ

^{disk of Sahno} which ^is _elongating

and

_undergoing a rearrangement ^{of its contents} preparatory to division.

With

careful study^it

was

found that nuclei were _present in different cells in this stage of metamorphosis.

The

irregularbroken granular threads

and

_granules observedin Fig. 1were seen, withcareful focusing, to have rearranged ^{themselvesin the}form of anintricate skein-like

meshwork

of threads, the directionof which

was

_generally

more

or less in conformitywith_{the long}axisof the nu- cleus. This stage corresponds very closely with similar preparatory stagesfig-ured

by Flemming and

^observed

by him

ⁱⁿ Salamandra.

Figs. 3, 4,

and

7represent other stages, alsopreparatoryor progress- ive. In_Fig.4 the nuclear matter exhibits atendency^to aggregate ^at the oppositepoles ofthe_nucleus,while_{in Fig.}3 aggregations^aretaking placearound the equator^of the nucleusaswell as at the _poles.

The

equatorial ring ofgranular aggregations^is viewed

somewhat

_obliquely, showing^thatthey occupya peripheralpositionagainst^itswall. Fig. 7 represents a nucleus ^{similar to}the _last,inwhich

we may

^likewisenote

the_equatorial

and

polar accumulations^ofnuclearmatter. Cleavage^or segmentation ^ofthecell willtake place^across the plane

marked by

^the

equatorial aggregations.

Other_phases inthis strangecycle of

phenomena

are represented ⁱⁿ Figs. 8, 11,

and

12. In _Figs. 8

and

12 the nuclear _equatorial plate seems tobe developed. In _{Fig. 11} the nucleus has_apparentlylost its contour, butiu allof thelast three the nuclear matter bas been_aggre- gated^intodefinitestout threads, withenlargements ^{at their}endsin two ofthecases.

In _{Figs. 5} and 6 the sharp contour of the nucleus has been _finally

lost; short, thick,

and

_{highlyrefringent} rods have been _develoi)ed on Bull. U.S.F. _0., 81 22

July

^{7, 1}

S82.

338 BULLETIN OF THE UNITED STATES

FISH COMMISSION.

either side of itsequator. In _Fig. 5 they areveryirregular; iu Fig. 6

much more

_regular.

Fig. 18 represents another phase ^of the progressive stage, inwhich the_refriugentnuclear rods at the oppositepoles of thenucleus forma loaf-like tigure. Inthis phase^{the rods}

seem

tobe about ready ^topart atthe equator^{so as to} assume the arrangement observed in Figs. 19

and

20. These are alsoprogressive

and

apiiroximating the^conditions

shown

in Figs. 13

and

15. Figs. _{14, 16,}

and

17 arestill furtherstages inthe process

and

indicate the stage

when

the cleavage ^orsegmenta- tion

may

^{besaid tohave been} completed. In _{Figs.9, 10,}

and

13 to_20, inclusive,^it

may

be observedthat the_refringentnuclear rodshave been aggregated^atthepoles ofthe_nucleus,where_theylieinabundlesome-

what

like a

bunch

of fagots, or in the formof a

crown

orwreath.

As

the polar crown-likefigures are separated the_refringent rods of which they^arecomposed^are

more and more

_{compacted together}intoacloser bundle, ^asindicated_{in Figs. 14, 10,}

and

17.

In_Fig. 21 the cleavage seems to have been _completed, as the two polar nuclearaggregations^lie

more

_nearlyinthe centersofthe

two new

cells. Thereis still atrace of therod-likeconditionofthe nuclearmat- ter discernible, but the tendency^is retrogressive, that_is, tothe phase indicated in Fig. ^2. This apparently completes the^{series of}rhythmical

phenomena

^which

we

have observed in the cleavage ^of thenuclei

and

cellsofthe germinal disk^ofthe

egg

^ofthe

common

salmon. In _Fig.21 the

two new

nuclei will undergo ^a retrogressive metamorphosis ^until they are^likeFig. 1;

when

this has been _done,they^will pass ^intothe so-called resting stage, only^torepeat the ^{series of}changes ^ofform

and

rearrangement^{of theirsubstanceiu}subsequent cleavages ^asdescribed above.

In

my

paper on the retardation of development ^{of the}eggs ^{of the} shad Ihave endeavored to explain

why

^it

was

^that segmentation ap- peared^togo onrhythmically; datasimilar totheseweretherelaidunder contributionto explain

away

^{the fact. I} had,uj) tothat_time,notbeen ableto

make any

observations of

my own

^on the behavior of the nu- cleusduring the ^acts of segmentation,

and

this notice is designed ^to supplement

and

reinforcethe arguments ^there put ^forth.

As

^{faras I}

am

aware, the foregoing account ^is the first which _minutelydescribes the behavior of nuclei iuthe segmentinggerminal disk ^ofanyfish,

and

forthat matter, the segmentation ^ofauy ^{ofthe cellsofa}teleostean.

The

_stages represented in Figs. 3, 5, 0, 7, 8, 11, 12,

and

18 appear^to represent, in successive order asnamed, ^thesystoleof thenuclear mat- tertowards the equator^ofthe_nucleus, while _{Figs. 18,} 20, 19, 10, 9, 13, 15, 14, IG, and17 _similarly

and

successivelyrepresent the <?mfo/e phases of repulsionfrom thenuclearplate or equator.

The

rhythmical nature of the

phenomena

can, ^I think, hardlybe questioned, nor^will auy one doubtthe propriety ^ofthe application oftheterms _systole

and

diastole as suggested

by

Flemming. ^Lestitbeobjected that the nuclearfigures

PLATE

XVIII.

5

9

w

12

.^-t

22 ₂₃

Nuclear cleavage figures of

Sai.mon

Eggs.

BULLETIN OF

FISH COMMISSION.

339

arethe result ofthe disturbing^effects of reagents, ^{let it} be remarked

liere that precisely similar cliauges have been observed in the_living nuclei ofboth plants

and

animals.

Xo

connecting granular ^fibers could, as a _rule, be _clearly

made

out between the aggregations ^at the opposite poles ofthe nucleus.

The

connecting lines,

when

_{present, appeared} tobe

more

or less brokenas represented ⁱⁿour _sketches,

and

_{only a}faint outlineofthe nuclearfield

betweenthe aggregations could be _clearly

made

out. Xeither

was

it ])0ssible to findany granular^linesradiating outwards from

and beyond

theends ofthe aggregations^intothesurrounding protoplasm^ofthecell inwhichthe nucleiwere embedded.

This condition is in very

marked

contrast withthat constantly ^ob- served inthe connective tissue-cellsof the _oyster, oneof

which

isrep- resented_{in Fig.} 22 enlarged 800 ^times.

Here

a complex network ^of granular threads passes outwards in all directionsfrom the _irregular nucleus throughthe envelopingprotoplasm; besides the threads there are usuallyoneor

two

_globulargranular accessory bodies present, as

shown

in the _figure.

A

still

more

complex arrangement ^of granular threads aroundthenucleus is

shown

in Fig.23 of a_cell, enlarged ¹,000 times, from the reproductive ^{tissues of} the smooth limpet, GrepirJnla (jlauca. Thislastfigure ^isfrom a sketch

made two

_{yearsago from}fresh material studiedin neutral fluid.

THE ]>£STRU€TfO]\ OF YOIJXG FISH BY

Ui\SUITABr.E

FISHINO

IMJPIiEMElVTS.

By

^{B. P.}

CHADWICK.

Bradfoed,

Mass., December_23,1881.

Prof.

Spencer

F.

Baird

:

Dear

Sir: Itakethis

method

of callingyour attention toa_subject that has occupied

my mind

^for a longtime,

and

that_is, the destruction of the

young

^fishalong our^coastfrom

Cape Henry

^to

Xova

_Scotia,

by

theuseof ill-constructed nets,pounds,weirs,

and

_trapsofeverydescrip- tion.

For

instance, in the seining^ofmackerel itoftenhappens ^that200 barrelsaretaken ata time; ^{of this}

amount

_{only 25}barrelsarefoundto be_largeenough ^to beof

any

^valueinthe market, the other 175 ^barrels arethrown backintothe _sea, all dead. This is a_daily occurrenceina hundred_places,

and

countlessmillions of

young

^fishare destroyed ^dur- ing the mackerel season annually.

The

catch of mackerel is of vast importance ^{to this} country, and the useless destruction of the

young

fishisfour times the

amount

of thatsold as food. This

wanton

waste of the

young

^{fish can all} be avoided

by

^{act of} Congress, compelling fishermentouse_seines,the

mesh

ofwhich islargeenough^forthe

young

of auselesssizeto pass through; thus there would be nofishtaken ex- cept suchas aremarketable. This _subjectisprobably nothing

new

to