THE EEL FAMILY. 439 



independently, three years later, by O. F. Miiller. In 1850 the 

 first mature eel which had come under observation was examined 

 by Rathke. The ovaries of the eel consist of two frill-like 

 bands extending the whole length of the abdominal cavity, 

 from the liver to beyond the vent. Each ovary is attached by 

 its dorsal or adherent edge to the peritoneal covering of the 

 swim-bladder and the upper part of the abdominal wall; its 

 ventral border is free. The colour of the ovary varies according 

 to the stage of development of the eel. In young eels 28'7 cm. 

 (11*5 inches) long, it is glassy in appearance, with a very 

 slight whitish tinge ; in larger eels the ovaries, crowded as 

 they are with eggs and fat spaces, are opaque and white in 

 colour. The main interest attaching to the female sexual 

 organs of the eel is the absence of any definite genital ducts, the 

 ova no doubt being discharged freely into the body-cavity and 

 from thence to the exterior by genital pores. This character is 

 believed by some authorities to be primitive. As regards 

 sexual diversity in size the eel appears to be no exception to 

 most bony fishes in that the males are considerably smaller 

 than the females. No male eel longer than 20 inches has been 

 recorded, whilst females are frequently more than 3 feet in 

 length. 



Much attention has been given to the attempts to find 

 external sexual differences in eels. Difference of colour, when 

 taken together with certain anatomical differences, was con- 

 sidered to be of value in the separation of the sexes. The male 

 was very often, invariably by Jacoby, found to have a metallic 

 sheen on the sides of the body. The females were as a rule of 

 lighter coloration on the back than the males. ' The snout of 

 the female is not only much broader, with more prominent 

 eyes, but is also more depressed, a characteristic to which I 

 would call special attention, and one which I do not find in the 

 male. In contrast, the snout of the male eel is more convex 

 By paying attention to the two most important characters, viz. 

 the relative proportions of the dorsal fin and snout, and, by their 

 help, picking out those specimens which appeared to be males, 

 I actually found 80 90 per cent, of those individuals so selected 

 to be males with the Syrskian organ.' 



