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NATURAL HISTORY 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. 



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 

 Eels, on an average, eight females, and two with the supposed male organ; but, if the selection is 

 made with a careful reference to all these marks of difference, the proportion changes, and out of 

 every ten examples about eight will be found with the supposed male organ.' 



For another excellent discussion with figures of the characters of male and female Eels, the 

 reader is referred to a translation of an article by S. Th. Cattle, in the Proceedings of the United 

 States National Museum, vol. iii, pp. 280-284. 



Eels supposed to be viviparous. — The discovery of the two sexes has not, however, writes 

 Benecke, settled the question whether the Eel lays eggs or brings its young alive into the world. 

 There has always been a strong disposition to adopt the latter hypothesis, and there are many peo- 

 ple at the present day who claim to have been present at the birth of young Eels, or to have found a 

 quantity of young Eels in adult Eels which have been cut open. Frequently ichthyologists hear 

 accounts of occurrences of this kind, and receive specimens of supposed little Eels, from one to two 

 inches in length, which have been kept alive for several days in a glass of water. These are usually 

 thread- worms, Ascaris labiata, which live by the hundred in the intestinal cavity of the Eel, and 

 which may be easily distinguished from the Eels of the same size by the sharp ends of the body, the 

 absence of fins, of eyes and mouth, and by the sluggishness of their motions. The smallest Eels, 

 less than an inch in length, have already the complete form of the adult, and axe also transparent, 

 so that with a magnifying glass one may perceive the pulsations of the heart, and see behind it the 

 brownish-red liver; the mouth, the pectoral, dorsal, anal, and caudal fins, are easily seen, and the 

 black eyes cannot be overlooked. In addition to the intestinal worms, the young of a fish of another 

 family, Zoarces viviparus, have given opportunity to the ignorant for many discoveries; for instance. 

 Dr. Eberhard, in No. 4 of the " Gartenlaube" for 1874, described and illustrated an " embryo of the 

 Eel," which, in company with about a thousand similar embryos, had been cut out of the belly of 

 an Eel. This tolerably good drawing at first sight is seen to represent the embryo of Zoarces, 

 which is almost 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 two or three hundred young in the Zoarces to a 

 thousand. 



'Jacoby: Der Fisohfang la der Lagune you Comacchio. 



