EXTEENAL CHAEACTERISTIOS OP THE SEXES. 



645 



The deferent canals and the genital orifice are closed in young Eels of the male sex, and open 

 simultaneously with the development of 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 in some of the smaller ones they were closed and in others open. 



f 9 h 



Fig. 7. — Piece of the testicle (one hundred and sixty times enlarged)^ 

 showing the vascular tissue and the small granules. 



!FlG. 8. — Anal part of the male Del, enlarged twice, 

 a. Straight intesiine. 



6. Fissura recto-vesicalis, covered by the out- 

 side wall of the semiEal pouch 



c, c. Outlet of the anterior and posterior part 



of the defefeiit canal in the pouch. 



d. 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 characteeistics. — 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"™). 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 



