G. Brown (George Brown) Goode.

The fisheries and fishery industries of the United States (Volume 1:1) online

. (page 108 of 146)
Online LibraryG. Brown (George Brown) GoodeThe fisheries and fishery industries of the United States (Volume 1:1) → online text (page 108 of 146)
Font size
QR-code for this ebook


all at once brought up the celebrated issue of the previous century ; this time, however, having
specially in view the male organs of the Eel. All were convinced that they had reached a
linal result by their investigations. The results were certainly very peculiar. In the paper of
Ercolani it was claimed that the snake-like folds of fat, which had formerly been noticed near the
ovarium, were nothing else than the spermaries of the Eel, and that upon the left side ot the animal

1 Jacoby. Der Fischfang in der Lagnns von Coniacchio. Berlin, 1880, pp. 23-30.

Robin, Comptes rendns, 1881, p. 383.

' Jacoby states that in a paper by Rathkr, published in 1838 in the Archiv fiir Xaturgetchichte, he remarked: "I
expect soon to be able to say something concerning the male organs of the Eel." It would be very interesting to
know whether in the papers left by this skillful investigator there may not have been recorded some valuable obser-
vations concerning the male Eel.



640 NATURAL HISTORY OF AQUATIC ANIMALS.

this organ developed into a true testicle, while the one upon the right side shrank up and became
functionless. In the work of Crivelli and Maggi, on the other hand, the folds of fat next to the
ovary were also considered to be the male organs of the Eel, while the one on the right-hand side
of the animal was considered without any doubt to be the male reproductive organ. The last-
named authorities described the spermatozoa which they had seen in this stripe of fat upon the
right side. Since these stripes of fat were universally found in all Eels, and always in connection
with the former, the investigators could come to no other conclusion than that the Eels were
complete hermaphrodites.

The male organ of the Eel, as described by Ercolani, as also by Crivelli and Maggi, shows
how carefully investigations may be expended upon things which are not in the least equivocal,
since there was not the slightest trace of structure like that of a spennary. The cells of this body
in the lining of the stomach next to the ovary are simply fat cells, with all the characteristic
peculiarities, just as they are given in all the manuals of histiology. Professor Rauber, of Leipsic,
has examined these fat cells carefully, and they have also been investigated in many Eels by the
writer, Dr. Jacoby. Never has anything but fat cells and blood-vessels been found in them. The
so-called spermatozoa, described in the work of Maggi and Crivelli, proved to be microscopic fat
particles or crystalline bodies, such as are commonly found in fat cells. 1

In the mean time, at Trieste, the question concerning the male organs of the Eel was making
a very important advance. Darwin had already expressed the opinion that among nearly all fishes
the female was larger than the male. He states that Dr. GUnther had assured him that there was
not a single instance among fishes in which the male was naturally larger than the female. This
opinion may, perhaps, have induced Dr. Syrski, director of the Museum of Natural History at
Trieste, now professor in the University of Lemberg, when he undertook, at the request of the
marine officials of Trieste, the determination of the spawning time of the fish which were caught
in that region, and was obliged to take up the eel question, to devote his attention especially to
the smaller Eels. Dr. Hermes, in behalf of Dr. Syrski, protests against this idea, stating, on the
authority of the latter, that the published opinions of Giinther and Darwin were unknown to him
prior to the publication of Jacoby's paper. Up to that time every investigator had chosen for
investigation the largest and fattest of Eels, thinking that the largest and oldest specimens must
have the most highly developed organs of generation. On November 29, 1873, Syrski found in the
second specimen which he investigated an individual fifteen inches long, which is now preserved
in the museum at Trieste a completely new organ, which had never before been seen within the
Eel by any former investigator, although tens of thousands of Eels had been zealously studied.*
Syrski published his discovery in the April number of the Proceedings of the Imperial Academy
of Sciences, Vienna, in 1874. 3 The most important point of the discovery was stated to be that,
in all the specimens of Eels in which the Syrskiau organ was found, the well-known collar-aud-
cnff shaped ovary, the female organ of generation, was entirely wanting. It was evident from
this that Eels were not hermaphrodites. The question now arose, is the newly discovered organ

'In a microscopic investigation of fatty tissnes it is very easy for the so-called Brownian molecular movements to
be mistaken for moving spermatozoa, especially in fishes, whose spermatozoa, if not very much magnified, show only
the head and appear like litt.Ie bod ies globular in form.

*"I commenced my investigations," writes Syrski, "on the 29th of November last year (1873), and already in the
second Eel which I dissected on that day I found the testicles, and therefore a male individual of the Eel. I sent in
March of the following year (1874) to the Academy of Sciences in Vienna a preliminary communication, which was
read at the public session held (he Kith April, and printed in the reports of the academy."

'In 1875, Professor von Sielwld found male Eels in the Baltic at Wismar, although this discovery was not at that
time made known to the public. They have since been found in the German Ocean, in the Atlantic, and in the
Mediterranean.



INTKKNAI. CIIAi:.\CTi:i;iSTIGS OF TI1K SKXKS. (541

in tlic Krl, iii its external form, as well as inner structure, so ditl'erent from the ovarv that it
could he considered as a partially developed or peculiarly shrunken ovaryf According to all
researches which lia\e u]> to tliis time been made there is the highest kind of probability that
this newly discovered structure is actually the long-sought male organ of generation. The inves-
tigator cannot, howexer, answer this question with complete certainty, since the thing which is
most necessary to the solution of this question, namely, the finding and the recognition of the
spermatozoa, has not yet been accomplished.

In February, l*7!t. Professor Packard announced the discovery of spermatozoa in Eels from
Wood's IIoll, Massachusetts, but soon after declared that this was a mistake, and that he had
been deceived by molecular movements among the yolk nuclei in the female organs. The discovery
of spermatozoa in the spermaries of the Conger Eel, recently announced by Dr. Hermes, of Berlin,
is, however, sufficient to demonstrate fully the correctness of Syrski's theory. The confirmation
in the case of the common Eel is solely a matter of time.

INTERNAL CHARACTERISTICS OF MALE AND FEMALE EELS. The differences between the
organs of sex in the Eel are well described by Benecke. The ovaries of the Eel are two yellowish
or reddish-white elongate organs as broad as one's finger, situated alongside of the backbone,
arranged in numerous transverse folds, extending through the entire length of the abdominal
cavity. They have no special opening to the outside of the body, and their contents must be
discharged into the abdominal cavity and must find exit through the very small opening situated
behind the anus. These two bodies, on account of their great size, are of course not easily over-
looked, but they contain such a great quantity of fatty cells and the eggs imbedded in them are so
.~mall and delicate that one might easily believe, even after a superficial microscopic examination,
that the whole organ consists only of fat. While the eggs of other fishes measure from one to three
millimeters in diameter, and sometimes are much larger, still the eggs in the ovary of the Eel have,
on an average, a diameter of about one-tenth millimeter, and are so closely surrounded by fatty
cells with outlines much more strongly marked that it requires great skill to prepare a microscopic
slide in which they shall be as plainly visible as they are in the accompanying illustration, in
which they are magnified one hundred and fifty diameters. When a person has a microscope
which magnifies only one hundred diameters, it is best to put a portion of tbe ovary in water when
dissecting it, in order that the eggs may be easily found. It is much easier to find the eggs in
young Eels, seven or eight inches in length, than in adult fish, since in the former, although the
ovaries and the eggs are smaller, the fat cells have not made their appearance, and the eggs are,
therefore, plainly visible at the first glance through the microscope. The number of eggs is extra-
ordinarily large, amounting to many millions. The eggs of larger size which sometimes are found
in great quantities in Eels that have been cut up, and have been considered to be eel eggs, have
always proved to be the eggs of other fish which they have swallowed, and in the course of cutting
them up have been found in the Eel's belly.

The male Eels, which are found only in the sea and in the brackish water, are much smaller
than the females, rarely exceeding fifteen or sixteen inches in length; in them, in the place of
the ovaries in the female, are found spermaries, which differ in appearance in the manner shown
in the illustration. These consist of two tubes which stretch the whole length of the body cavity,
situated close to each other, and provided with numerous sacculations. Ripe spermatozoa are
as rarely found in these organs as eggs ready to be laid have been found in the ovaries of the
female. According to many accounts the male Eels, which later were found also by von Siebold
in the Baltic Sea at Wisuiar, differ from the females in the possession of a proportionally sharper



642



NATURAL HISTORY OF AQUATIC ANIMALS.



snout, less conspicuous dorsal fins, darker coloration of the back, a more prominent and metallic
luster upon the sides, the clean white coloration of the belly, and the larger size of the eyes. I
propose to reproduce here the original descriptions and figures of Syrski, the discoverer of the
male Eel.

Having met, writes Syrski, with many errors regarding the female organs of reproduction

in the descriptions hitherto given of them, I intend to commence
by describing these organs, first with the view of rectifying and
completing the details, and also for the purpose of comparison
with the male organs.

THE OVARIES OF THE EEL. The organs (Fig. 1) two in num-
ber, are ribbon-shaped, with leaflets on their outer face, and with
transverse folds. In the natural position of the live fish, the
one extends to the left and the other to the right of the aliment-
ary tube, following most of its angles nearly the whole length of
the abdominal cavity to the place where the dorsal parietes are
confluent with the lateral.

The right ovary commences at a point nearly corresponding
to that where on the outside the right pectoral fin ends, and the
left ovary commences about two centimeters and ends three to
four centimeters behind the former. They extend three to six
centimeters back of the anus, into the caudal part of the animal's
body; they do not, however, unite in a single body, as some
have asserted, but both are toward the end inclosed in a perito-
neal membrane, and are separated from each other by the union
of these membranes, having each on their inner face an accessory
ovary (pars recurrens ovarii). , In rare cases is such an accessory
ovary wanting either on the right or on the left side.

The ovaries in fully grown Eels are in the middle about two
centimeters larger, and posteriorly terminate in a thread-like
form. They are not smooth on both sides, but have, as was said
above, on their outer side numerous transverse folds (Fig. 2) full
of eggs (Fig. 3).

It is another of Rathke's erroneous assertions, likewise main-
tained by others, that the genital opening through which the
eggs pass out from the abdominal cavity is formed by two holes,
a right one and a left one. I have invariably found in all speci-
mens examined a simple hole, which communicates with the right
and left half of the abdominal cavity by means of a transverse
fissure between the straight intestine and the urinary bladder
(Jumura recto-vesicalis) and opens in the urethra (Fig. 4).

It is generally admitted that the eggs, when loosened from
the ovaries, fall indiscriminately into the abdominal cavity, but it
is not said which way they take in order to go out through the
genital aperture. As I have invariably found that the fully developed ovaries lean with their outer
surface against the side of the abdominal cavity, and approach with their free edges the lower
lortioii of this side, forming, so to speak, a furrow, I must conclude that the loosened eggs



I-*



Fin. l.-Ftmatr Eel, lonffitndiiuil uelion of the
filnitijnfn; natural rizf.

a. Ki<:ht ovary.

b. Left ovary.

e. \ rri'ftnory part of right oviry.
d. I,rfl lUTrHMiry part.
Dividing membrane.
/- A nnl <! jn fKNinn .
a. Vrinarv bladder.
h. Kat on I lie right nidc. erroneonnly
taken for the testicle* by Home.
A'. Similar fat covering the stomach.
i. Kat "ii the left aide.
Jr. Stomach.
I 1 ' . Iciiui.
m. Liver,
n Kall-bladder.
o.o. Pectoral Una.



OVAKIKS OK TIII-: 1:1:1..






descend between the abdominal partition and tb folds ntxl leaflets of the ovary in the above-men-
tioned furrow-, and from it pass to tin* genital aperture without scattering in the abdominal cavity.




Flu. 2. I*ifer of thf ovary, drier in natural tilt, mtk
ovarian Itajtrtt arranged in trarttvertal rotot,
on it* twrfae*.

Thn Rtiortxr Imrdcr atUchwl to the ilnrnal wll
of the abdominal cavity ; the longer
froe.




Flo. 3. ri



etc of a Kitnrtchat (trrebtptd orary. one hun-
dred titnn the natural lizr. ,h:-winy the trant-



,

parent rggi tritr, thr yerminatire
tkr germinalier dutt.




Flo. 4. Anal part of a female Eel, twice thenaturaltize.
./. Straight intratinr.
6. Fiiwura mrto-rfalc.ilia.
r. Urinary bladder.

(/. Ann*.
e. Partition.



As to the development which the ovaries undergo, I have observed from the end of Noveml>er
till the beginning of March, in many adult Eels, of the length of 530 millimeters and more, that
4 / g the ovaries were of the breadth of fifteen to twenty-five
. millimeters, and of a yellowish and sometimes reddish-
white color, produced by the development of adipose tissues
and of the blood-vessels and not by the eggs filled with
little globules of fat; the genital aperture and the fissura
recto-vesivalis were open.

In other Eels, of a length sometimes of 600 millimeters
and more, I found the ovaries less broad, with but little fat,
and of a mucous and almost glassy appearance, so that I
could discern the so-called vesicles and germinative dots
(nuclei and nucleoli); the genital aperture and the fissitra

/ tJroKrnital ojK-ning.

g. Outlet of the c?n>Ul opening in the urethra. rectO-VCSlCanS Were Closed.

The ovaries of young Eels, of the length of about 500 millimeters, contained invariably
but little fat, and the eggs were without globules. The gradual growth and enlargement of
the ovaries go on simultaneously with the opening of the genital orifice. According to the quan-
tity of fat contained in the ovaries, they have a mucous and glassy, or more or less opaque or
white, appearance, or have small shining dots. From the end of March till October I found in the
majority of Eels which I examined, measuring COO to 700 millimeters in length, that the ovaries
were scarcely white, and that the genital aperture was closed. The number of egg contained in
both developed ovaries reaches, according to my calculation, five millions. The larger eggs
measured by me had a diameter of one-fourth to one-fifth millimeter, while the eggs of an adult
'Grongo' (Conger) had, according to my measurements, a diameter of one-third of a millimeter,
and those of the 'Mureua' (Muratna helena) almost one millimeter, which explains to me why the
ovaries of the two last-mentioned species of fish have long since become known.

In an Eel measuring 51)0 millimeters, examined on the 6th July, the left ovary was entirely
wanting, and replaced by a mass of fat.

THE SPERMATIC ORGANS. The position of these organs (Fig. 5), which are not ribbon-
shaped like the ovaries, but represent two longitudinal rows, each \\ iih about fifty lobules (Fig. 6),
of the width at most of three millimeters, and found only in Eels not more than 1:50 milli-
meters long, corresponds entirely with that of the ovaries. In these organs are likewise found



644



NATURAL HISTOEY OF AQUATIC ANIMALS.



A



toward the posterior end, the spermatic organs (paries recurrentes), which, however, as is the case
with the ovaries, are sometimes wanting.

The spermatic organs can be distinguished at the first
glance from the ovaries of the adult Eels and those of the
young Eels, not only by their lobular form, but also by their
shining, glassy appearance, by the surface of the individual
lobes, which is smooth and without leaflets, and by the much
greater density of the tissue, so that with a pair of pincers one
can take off a large portion of the organ, which could not
possibly be done with a more developed ovary whose tissue
is as tender as a cobweb, and is composed of small vessels
formed of a thin membrane and filled with eggs and fat.

The fibrous tissue of the spermatic organs is composed
of vascular compartments with thicker partitions, inclosing,
according to the development of the organ, granular
globules (Fig. 7).

These compartments are joined toward the inside and
the base of the lobes, which are united to a tube (vas deferens),
which, cajcal at the commencement, runs along the entire
length of the abdominal cavity, and opens near the straight
intestine (rectum) in a triangular pouch, which likewise con-
tains a vas deferens starting from the caudal part of the
spermatic organ. This pouch has its outlet in the general
orifice, which opens in the urethra (Fig. 8).

As regards the development of the spermatic organs, I



I e






Flo. 5.- Jfofe Eel (naturalize).
a. Ubl.t testicle.
6. I.- li tent id .
e. Right IHT.-M-.OIV part,
d. l.-ft a<-o-HHt y part.
. Dividing membrane.
/. Df*n>nt ranal.

. Seminul pouch.
. Anal ilrpn-HMion.
i t"riniry bladder, covered to a great extant

by th" aimiinal poncd.
k Fat <m th \\v\it aide.
k . Simil ir fat . nv.-i um the stomach.
1. Fat on the left aide.
m. Stnti nrh.
n. I'yiornfl.
v I.i\ i-i . turned up to show the inner Biirface




FIG. 6. Three lobet of the right teiticle, mth the deferent canal (enlarged ten times).

a. Lobes, Been from their outer surface.

b. Lobe, seen from HH inner aurfoce.

c. Deferent canal.

d. Anterior part of the same.



have observed that the lobes of these organs in young Eels,
measuring not more than 200 to 300 millimeters in length,
are not yet very distinct, forming two thin ribbons differing
but little from ovaries of the female in their average size. In

*" the <E ' opl "' 1!U8 aml the Eels measuring about 400 millimetersiu length, the testicles
can easily be distinguished from the ovaries. The former,
much straighter, and with tissue, as has been already remarked, much more solid, are provided
with a much more developed net- work of vessels; their lobes are very distinct and the deferent
canals are usually open, while the ovaries present the appearance of two continuous ribbons,
have a more delicate tissue, and an almost mucous appearance, and contain the eggs with the
geruiinative vesicles.



p. Gull-bladder.
9, 9. Pectoral fins.



HXTI:I;NAI. CIIAI;.\CTI:I;ISTICS OK TIIK SKXKS.



The clHVivnt ranals an.l tin- -.tiital orifice nre closed iu young Eels of the male sex, and open
simulta isly with the <h-\ cl(p|uiiciit <>!' the lobes.

In the male Eels examined by me from March to October I have found individuals, of 400
millimeters and more in length, whose genital orifice and deferent canals were invariably open,
while 111 some of the smaller ones they were closed and in others open.






\f//





Fio. 7. Piter p/ the trtlitlt (on* hundred and lixly timei enlarged),
ihomny the tateular titeu* and the mall granule*.



Fio. B.Anal part of the male Eel, enlarged tirire.
a. Straight intent inc.
ft. FiHHurn rt-rto-vfHicaliii, oxiven-d liy th out-

itiilr wall of tin- Hi-tniDal i><m. li
e. e. Outli-t of tho anterior and poMcrior part

of tin- ilrfflrnt lUlial Iu till' pouch.

t. Urinary bladder.



Of the 258 Eels examined by me, the males and females were in about even proportion ; the
greatest length of the former was about 430 millimeters, while the latter were of all sizes up to
1,050 millimeters, which shows that the males are smaller than the females.

EXTERNAL CHARACTERISTICS. The external differences presented by living Eels (remarks
Jacoby), corresponding to the presence of an ovary and the supposed male organ, are very inter-
esting.

The most important, writes Jacoby, is (1) the difference in the size and length of the animal.
Syrski states that the largest Eels found by him with the supposed male organ measured about
17 inches (430 min ). I have, however, found specimens with this organ at Trieste and in Comacchio
which measured 17 to 19 inches (450 millimeters to 480 millimeters). All the Eels which exceeded this
size, for instance those which were over three feet in length (one millimeter) many of them growing to
the thickness of the arm of a strong man, have been hitherto found to be females. The other recog-
nizable external characters in the female are (2) a much broader tip of the snout in comparison
with the small, either attenuated or short and sharply pointed, snout of the Eel with the supposed
male organ ; also, (3) a clearer coloration in the female, usually of a greenish hue on the back, and
yellowish or yellow upon the belly, while the others have a deep darkish-green, or often a very
deep black upon the back and always a more perceptible metallic luster upon the sides (I, once in
a while, found Eels covered all over with a brownish tint, always possessing the organ of Syrski),
usually exhibiting also a white color upon the belly. In addition (4) there is an important external
character in the height of the dorsal fin ; all females have these fins much higher and broader
than the Eels of the same size which possess the supposed male organ. Finally, (5) there is a
character, which is not always a safe one, in the greater diameter of the eye in the Eels with the
supposed male organ. Eels with quite small eyes are almost always found to be females ; Eels
with the organ of Syrski usually have comparatively large eyes, yet female Eels with quite large
eyes are not unusual.

The following proportional measurements, the average results of the study of a great number
of Eels measured by me, will be of general interest. Column a gives the total length of the Eel;
b the breadth of the snout between the nostrils; c the breadth of the snout between the eyes; d
the length of the snout from the center of the eye to its tip; e the average measurement of the



646



NATURAL H1STOKY OF AQUATIC ANIMALS.



eyes; /the length of the head to the gill-opening; g the height of the dorsal fins, all the measure-
ments being given in millimeters.





A. Eels with supposed male organ.


B. Female eels.






a.


b.


c.


d.


t.


/.


g-


a.


b.


c.


d.


e.


/


g-




I


480


<


13.5


15


8


52


5


480


8.5


12


17


5


62


9


I


II


470





10.5


12


7


54


a


475


7.5


14.5


16


8


59


9.5


n


m


445 5


11


12


6


47


6


440


8


12


14


r>


56


7.5


in


IV


411


4





12


5.5


47


6


410


8


12.5


13


7.5


51


7


IV


V


386


4.5


9


12


5.5


46


4


378


7.5


11


12


5


49


7.5


V


VI


370


3.5


7


10.5


5


40


6


MB


7.5


11


13


6.5


51.5


7


VI


VII


344


4


7.5


10


4.5


40


5


342





8


11


4.5


44


0.5


VII


VIII


319


4


7


10 ; 5


40


4.5


313


5.5


8


10.5


3.5


41


6


vra



According to the distinguishing marks which have been given, special reference having been
paid to the height and narrowness of the dorsal fin, much success has been met with in picking
out, in the fish-market of Trieste, the Eels which possessed the organ of Syrski; absolute certainty
in recognizing them cannot, however, be guaranteed. If one is searching among living Eels with
no characters in mind with the exception of the first that of length he will find in every ten



Online LibraryG. Brown (George Brown) GoodeThe fisheries and fishery industries of the United States (Volume 1:1) → online text (page 108 of 146)