112 



FOREST AND STREAM. 



[Mabch 9, 1882, 



ink) Hie abdominal cavity and must find exit thrailgh the 

 very smnll opening .situated behind the anus. These two 

 bodies, on account of their great size, are of course not easily 

 overlooked, hut they contain Such a great quantity of fatty 

 cells and the eggs imbedded in them are so small mid delicate 

 that one might easily believe, even after a. superficial micros- 

 copic examination, that the whole qygah consists 1 ojily O'f fat. 

 "While the eggs of other fishes measure from one to three millc- 

 rnetcrs in diameter— and sometimes are much larger — still 

 the eggs in the ovary of the eel have, on an average, a di- 

 ameter of about one millcmeter, 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 arc in the accompany- 

 ing illustration, in which tlicy are magnified 150 diameter's. 

 When a person has a microscope which magnifies only 100 

 diameters, it is best to put, a portion of the ovary in water 

 when dissecting it, in order that the eggs may" lie easily 

 found. It is much easier to Hud the eggs' m voting eels. 7 or 

 8 inches in length, than in the 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 (he first glance through thVimorcseop: Tic 

 numlier of eggs is extraordinarily large, amounting to many 

 millions. The eggs of larger si ze, which sometimes arc 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 

 coarse 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 15 or 16 inches in length; in them, in the place of 

 the ovaries in the female, are found spermaries, which differ 

 in appearance in the manner heretofore referred to. 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 tin: 

 male eels, which latter were found "also hv Von Skbold in 

 the Baltic Sea at Wismar, differ from the. females in the pos- 

 session of a proportionally sharper snout, less conspicuous 

 dorsal fins, darker coloration of tie 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 re- 

 produce here the original descriptions and figures of Syrski, 

 the discoverer of the male eel. 



EXTERNAL CHARACTERISTICS. — JACOBY. 



The, external differences presented by living eels (remarks 

 Jacoby), corresponding to the presence' of an ovary and the 

 supposed male organ, are very interesting. 



The most important, writes" Jacoby, is (1) the difference in 

 the size and length of the animal." Syrski states that the 

 largest eels fouutl by him with the supposed male organ 

 measured about 17 inches, 430 mm . I have, however, found 

 specimens with this organ at Trieste and in Comaeehio which 

 measured 17 to 19 incites, 450 to 480°"". All the eels which 

 exceeded this size, for instance those which were over 3 feet 

 in length, lm, many of them growing to the thickness of the 

 arm of a strong man. have been hitherto found to be females 

 The other recognizable external character in the female are 

 (3) 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) it, 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 attd 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 addi- 

 tion (4) there is an important external character in the height of 

 the dorsal fins; all females have these fins much higher and 

 broader than the eels of the same size which possesses 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 arc almost, always found to be females; eels with the 

 organs of Syrski usually have comparatively large eyes, yet 

 fernnk' eels with quite large eyes are not unusual. 



The following proportional measurements, the average re- 

 sults 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 ;/> the breadth of the snout, between the nostrils; c 

 the bredth of the snout between the eyes; d the length o'f the 

 Snout from the centae of the eye to "its tip; <• the average 

 measurement of the male eyes;. f the length of the head to 

 the gill-opening; g the height of the dorsal fins, all the meas- 

 urements being given in millemeters. 





A. Eels with supposed male 







organs. 







a, | b. c. d. 



* ! /■ 9- 



1 



a. 



b. 



c. 



cl. 



e. ' /. 9. 



I 



48H 6 ! 13.5! 15 



8 53 5 



4RI) 



8 5 



n 



17 



5 03 9 



u 



470 i 10,5 13 



7 ' 54] (i 



475 



7 5 



U li 



10 



8 59 9.5 



111 



445 



5 11 18 



(i ! 47 1 



440 



8 



13 



14 



5 50 7.5 



IV 



111 



4 12 





fi 



410 8 





13 



7.5 51 7 



V 



:>si: 



4.5 3 13 





1 



378 ' 7 5 



li 



12 



.-) 49 7.5 



VI 



:;-. 



3,5 7 10.5 



5 40 



r. 



.100 7 5 



11 



13 



6.5 51.5 7 



Ml 





I : : to 



4,5 40 



5 



342 a 



H 



II 



4.5 11 5 



vin 



31!) 



■! r 10 



5 40 



1.5 



318 5.5 



8 



1,5 



3.5 41 I G 



According to the distinguishing marks which have 

 been given, special reference having been paid to the, height 

 and narrowness of the dorsal I'm. much success has been met 

 with in picking out, in the firsh -market of Trieste, the (-els 

 which possessed the organ 0f Syrski; absolute certainly in 

 recognizing them cannot, however, be guaranteed. If one 

 is searching amoug living eels with no characters in mind 

 with ihe exception of the first— that of hngth -he will Bra 1 

 in every ten eels, on an average, eight females, and with the 

 supposed male organ; bui if the selection is made, with a 

 careful reference to aU these marks of difference, the pro 

 portion changes, and out of every ten examples about eight 

 will be found with the supposed male organ. 



Pot another excellent discussion with figures of the Char- 

 acters of male and female eels, the reader Is referred to a 

 translation of an article by B. Th. Cattle, ill the Proceedings 

 o. the l. 8, National Museum, vol. iii, pp. 280-84. 



QJ L.-LION AH, TO TUE VIVIPAROUS NATURE OP EELS. — 



RENECKE. 



The discovery of Ihe two sexes has not, however, writes 

 Benccke, settled the question whether the eel lays eggs- or 



i ; alive into the. world, There h;is always beet! 



a strong disposition to adopt the latter hypothesis, and there 



are many people at the present, day who claim to have 



present at the birth of yc 



of yonng eels in adult'ci 



quenlly ichthyologists b 



kind, and receive spBoin 



to two inches in length, 



ral days in a gh 



Amm Uhmta 



cavity Of theci 



the eels of the 



absence of i 



4s, or to have found a, quantity 

 4s which have been put open, Fre- 

 lear accounts of occurrences of this 

 tens of supposed little eels from one 

 n length, which have been kept alive for seve- 

 ns of water. These are usually thread worms, 

 which live by the hundred 'in the intestinal 

 1, and which may be easily distinguished from 

 same size by the" sharp ends of the body, the 

 of eyes and mouth, and by the sluggishness 

 of thou- motions. "The smallest eels, less than an inch in 

 length, have already the complete form of the adult, and are 

 also transparent, so that with a magnifying glass one may 

 perceive the pulsations of the heart, and sec behind it the 

 brownish-red liver; the mouth, the pectoral, dorsal, anal, and 

 caudal fins are easily 



:annot be over- 

 utestinal worms, the young of a 

 38 vu-ip'iri's, have given oppor- 

 iny discoveries; for instance, Dr. 

 Gartfirimde for 1874, described 

 of the eel," which, in company 

 ibout a thousand similar embryos, had been cut out of 

 f an eel. This tolerably good drawing at first 



looked. In addition to the 

 fish of another family, Zoai 

 tunity to the ignorant for n 

 Aberhard, in No. 4 of th 

 and illustrated an "embry 

 witl 

 1 he 



sight is seen to represent the embryo of zoarccs which is al 

 most ready for birth, since it still possesses a very minute 

 umbilical sac. It is very evident that the minute egg of the 

 eel could hardly produce, a great embryo with an umbilical 

 sac which exceeds by more than a hundred times in size the 

 whole egg. It is also evident that the imagination of the 

 writer had exaggerated the 200 or 300 young in the zoarces 

 to a thousand. 



IICNT FOR YOI'NG EELS.— JACOBY. 



As might, have been foreseen, continues Jacoby, Syrski's 

 discovery drew attention anew to the solution of the eel prob- 

 lem. Iii the spring and summer of 1877, the German and 

 Austrian papers and journals were full of articles and para- 

 graphs upon this subject. Among others the following 

 announcement made the rounds of the press: "Hitherto, in 

 spite of all efforts, science has not succeeded in discovering 

 the secret of the reproduction of the eel. The German 

 Fischerei Verein in Berlin offers a premium of fifty marks to 

 the person who shall first find a gravid eel which shall be 

 sufficiently developed to enable Prof. Virchow in Berlin to 

 dissipate the doubts concerning the propagation of the eel. 

 I [err Dallmer, of Schleswig, inspector of fisheries in that 

 province, offered to transmit communications to Berlin, and 

 in 1878, in the January number of the Germ<tn Fishery 

 Gazette-, he published a detailed and very interesting report of 

 his proceedings. He wrote, among other things, that it was 

 quite beyond his expectation that this announcement would 

 have found its way into nearly all the German journals 

 between the Rhine and the Wcichsel, and from the Alps to 

 the sea. The number of •letters which he received first 

 rejoiced him, then surprised him, finally terrified him, so 

 that at last he was obliged to refuse to' attend to the com- 

 munications. He had learned at Berlin that an equal num- 

 ber of communications from all parts of Germany had been 

 received, sent directly to the address of Prof. Virchow. 

 Objects which professed to be young eels cut out of the 

 parents, but which were really thread worms, were sent to 

 him by dozens; the most incredible stories, usually from 

 women, about great, thick eggs which they had found in 

 eels, were received by him. A witty Berliner communicated 

 to him in a packet sent by express the information that the 

 eel problem was now happily solved since a lady eel in Berlin 

 had given birth to twins. Finally Herr Dallmer found him- 

 self compelled to insert the following notice in the Schks- 

 irir/cr Jsaehn'chten: 'Since the German tFischcrei Verein has 

 offered a premium for the first gravid eel, the desire to 

 obtain the prize, curiosity, or the desire for knowledge has 

 created so lively an interest upon this point, that it might 

 almost be called a revolution. I at one time offered, when 

 necessary, to serve as an agent for communication, but since 

 business' has compelled me to be absent from home a great 

 part of 'the time, I would urgently request that hereafter 

 packages should he sent direct to Prof. Virchow in Berlin. 

 I feel myself obliged to inform the public upon certain 

 special points. The premium is offered for a gravid eel, not 

 for the contents of such an eel, since if only these were, sent 

 it would be uncertain whether they were actually taken from 

 an eel. The eel must always be sent alone; the majority of 

 senders have hitherto sent me only the intestines or the sup- 

 posed young of the eel, which were generally intestinal 

 worms; the eel itself they have eaten; nevertheless the prize 

 of fifty marks has been'expected by nearly all senders, etc. 

 By this transfer of the responsibilities, the inspector of fish- 

 erics hits rendered a very unthankful service to Prof. Vir- 

 chow; he was obliged to publish a notice in the papers in 

 which he urgently stated that he wished to be excused from 

 receiving any more packages, for he would hardly know 

 what, to do with I hem.' The comic papers of Berlin now 

 circulated the suggestion that hereafter the eel should be sent 

 to the investigators only in a smoked state. This amusing 

 episode is interesting in showing how remarkable an interest 

 the whole world was beginning to take in the eel prob- 

 lem," 14 



UNDOUBTED NORMAL REPRODUCTIVE HABITS OF THE EEL. — 

 UKNT.CKE. 



It may be assumed with the. greatest safety, writes Benecke, 

 that the eel lays its eggs like most other fish, and that, like 

 the lamprey, "it only spawns once and then dies. .\]| the 

 eggs of a female eel show the same degree of maturity, while 

 in the fish which spawn every year, besides the large eggs 

 which are ready to be deposited at the next spawning period, 

 there exist very many of much smaller size, which are 

 destined to mature hereafter, and to be deposited in other 

 year-. It is very hard to understand bow young eels could 

 find room in the body of their mother if they were retained 

 until they had gained any considerable size. The eel embryo 

 can live and grow for a very long time supported by the little 

 yolk, but when (his is gone il can only obtain food outside of 

 the body of it- mother. The following circumstances lead 

 us to believe Chat the spawning of ihe eel takes place only in 

 the .sea: (11 thai the male eel is found only in the Sea or 

 brackish water, while female eels yearly undertake a pilgri- 

 mage from the inland waters to the sea. a circumstance which 

 lias been known since the time of Aristotle, and upon the 

 knowledge of which the principal capture of eels by the use 

 of fixed apparatus is dependent ; (•.') thai the young eels with 

 the greatest regularity ascend from the sea into the rivers and 

 lakes. 



All statements in opposition to this theory are untenable, 



14 Zoologischer Aazeiger, No 80, p. 103: American Naturalist, vol. 

 13, p. 185, and J««oby, p. 44. 



since the young eels never find their way into land locked 

 ponds in the course of their wanderings, while eels planted 

 in such isolated hodies of water thrive "and grow rapidly but 

 never increase in numbers. Another still more convincing 

 argument is the fact that in lakes which formerly contained 

 many eels, but which, by Ihe erection of impassable weirs, 

 have, been cut off from the sea, the supply of eels has dimin- 

 ished, and after a time only scattering individuals, old and 

 of great size, arc taken in them. An instance of this sort, oc- 

 curred in Lake Mi'iskendorf, iii West Prussia. If an instance, 

 of the reproduction of the eel in fresh water could be fouud, 

 such occurrences as these would be quite inexplicable. 



In the upper stretches of long rivers, the migration of the 

 eels begins in April or May," in (heir lower stretches and 

 shorter streams, later in the season. In all running waters' 

 the eel fishery depends upon the downward migrations; the 

 eels press up the streams with occasional halts, remaining 

 here and there for short periods, but always make their way 

 above. They appear to make the most progress during dark 

 nights when the water is troubled and stormy, for at. this 

 time they are captured in the greatest, numbers.' It is prob- 

 able that after the eels have once returned to the sea, and 

 there deposit their spawn, they never can return into fresh 

 water but remain there to die." A great migration of grown 

 eels in spring or summer has never been reported, and it ap- 

 pears certain that all the female eels which have once found 

 tiieir way to the sea are lost, to the fisherman. In Xo. 8 of 

 the German Fiseherei Zeilung for 1878, Dr. Schools published 

 certain statements sent to him by Dr. Jacoby. It is remarked 

 in this paper, among other things, that after the deposition 

 of the spawn, the female eel dies a physiological death, and 

 that occasionally the sea in the neighborhood of the mouths 

 of rivers has been found covered with dead eels whose ovaries 

 were empty. "When, where, and by Whom this observation 

 was made, and who pronounced upon the empty ovaries in 

 these deatl fish is unfortunately not mentioned. 



A great, number of the eels remain in inland waters while 

 others proceed to the sea, either because their eggs are at this 

 time sufficiently ripe, or perhaps because they are sterile. It, 

 would seem probable that the increase in t lie' size of the eggs 

 in the wandering eels begins to be very rapid after August, 

 and September, while ihthe earlier months of the year, in 

 all eels of moderate size, the eggs were, at the utmost but, 

 about 0.09 in diameter. In September of the same year, I 

 found (as an average of numerous measurements) a diam- 

 eter of 0.10; in October, 0.16; in November, 0.18 to 0.23, 

 while the eggs showed other characters connected with ap- 

 proaching maturity which earlier in the season were not to 

 bo seen. All the eels which were captured later— in Decem- 

 ber and January — part of which came from rivers and har- 

 bors, part from the harbor of Putzig (Putziger "VViek) had 

 eggs measuring from 0.00 to 0,09 mm , while, very exception- 

 ally, some measured '0.16™™, altkciugh among 'the fish ex- 

 amined were some which measured 3 feet iu length. 



DO MALE EBBS LEAVE TUE SEA AND ENTER FRESn WATER. 



This problem is one of great interest, both to ihe biologist 

 and fisbculturist — it is in "fact this one disputed point still 

 remaining to be solved. Upon its solution appear to depend 

 the final decision of the question still so warmly debated 

 both in Europe and America. "Do eels breed in fresh 

 water only, iu salt water only, or in both fresh and salt, 

 water." As has already been stated, the theory for a long 

 time generally accepted, is that eels are "catadromous," des- 

 cending to the sea to spawn. The theory is, however, sharp- 

 ly contested by many observers, chief among whom on Ibis 

 side of the Atlantic i's the lion. ' Robert B. Roosevelt, Presi- 

 entofthe American Fishcultural Association. It, appears 

 probable to the writer that the truth lies somewhere.', between 

 these two extremes, and that it will be hereafter ascertained 

 that the eel, like a majority of other animals, has tlcxibe habits, 

 sometimes deviating from its ordinary custom, which appears 

 to be to spawn in salt or brachial water. 



Male eels have been found in the following localities: 



1. In 1774 \ij Syrski, in the fish markets of Trieste; these 

 markets being supplied with eels fram Chrog.gia on the Adri- 

 atic, and to a lesser extent from the lagoons of Conimac- 

 chio. 



2. In 1875, on the coasts of France, by Darcstc. 



3. In 1875, among specimens of AiiguiJla marmarata from 

 India, 



4. In 1875, in the Baltic, at Wismar, on the Danish coast, 

 by Prof. Von Siebold. 



' 5. In 1877, in the lagoons of Commachio, by Jacoby. 

 Amougl,200 specimens, live per cent, were males; while 

 among these, less than 15 inches in length, 20 per Cent, were 

 males': This was in brachial water. (See paragraph XIX.) 



6. In 1879, at Trieste, by Dr. Hermes, who found 15 

 males among 20 eels selected by Dr. Syrski'. 



7. In 1880, on the Baltic "coasts of Denmark, by Dr. 

 Hermes. Out of one lot of 39 from "Wismar, he obtained 8 

 males, thus repeating Von Siebold's observation. 



8. In 1880, from the Baltic between Zealand and Saland 

 Denmark. Out, of one lot of 38, Dr. Hermes obtained 

 males. 



9. In 1880, in France, by Robin. 



10. In 1880, by Cattet. ' 



11. In 1880, by Dr. Hermes, at Cumlosen, on the Elbe, 

 about 1 20 miles from the German Ocean. 



12. In 1880, at Rugcrs on the Baltic, by Dr. Hermes, who 

 found 1 1.; per can. males in ohelof of L37. 



13. By Dr. Pauly, among eels planted al llumiigcn, in 

 Elsass-Lothringen. See below. 



It has! been shown by Dr. Pauly (hat among tie- vi-ry 

 youngeels (mono'), taken near ihe mouths o\' the rivers, is a 

 considerable percentage of males, which, when transplanted 

 to fresh water, will then retain their masculine characters 

 and develop into perfect adult male-. Thif discovery is, of 

 course, of the utmost importance to lisheult mists, ruaking 

 the attempt to introduce eels into new waters, Its importance 

 has already been pointed out by Director Haack. 



The practical lesson io be learned is Simply tins— thai 

 young, for introduction Into strange waters, iiufll be taken 

 from very near ihe mouths of river.-, in ord( r that both males 

 and females may be secured. The intaresl to soologiste ifes 

 in the fact that Pauly's discovery renders the theory of yon 

 Siebold less plausible, indicating thai the sexes of the young 

 eels arc differentiated before they begin to mount the rivers, 

 and thai Ihe males do not ascend beyond ihe limits of in-ack- 

 ish water. 



Dr. Pauly's di-covery is so interesting I hat I propose to 

 translate his own account of it. The investigation was made, 

 1 believe, in .Munich, and the report from which I quote was 

 published in the Austro- Hungarian Fish;-,!/ <j,i;, He, at Vienna, 



December 33d, 1880i Dr. Pauly writes; '-Dm , 



year I have received from Court-Fisherman Kuffar a large 

 .-els, which 1 have used in my inv, 



