LIFE HISTORIES 351 



fathoms, and probably much more. The males, however, as 

 stated above, continue to live in the aquarium for months after 

 their reproductive organs are perfectly mature, and their ulti- 

 mate death seems in no way hastened by the artificial conditions 

 of their captivity. 



The larva of the conger has been known to naturalists 

 since 1763 under, the name of Leptocephalus morrisii. It is a 

 small transparent fish, much compressed from side to side, broad 

 in a vertical direction, with a proportionally small head, from 

 which last character the name Leptocephalus, meaning " small 

 head," was suggested. The median fin is narrow, the pelvic fin 

 absent, the pectorals small. A large number of specimens of 

 this curious type were obtained from different parts of the world 

 and described as distinct species, but in 1864 the American 

 naturalist Gill came to the conclusion, for anatomical reasons, 

 that the Leptocephali were the young stages of the eel family, 

 and Leptocephalus morrisii in particular was the larva, of the 

 conger. The truth of this conclusion was placed beyond a 

 doubt by the French zoologist Yves Delage, who obtained a 

 living specimen of the creature in question at Roscoff in Nor- 

 mandy, in February, 1868, and kept it alive till the following 

 September. Between April and July the Leptocephalus under- 

 went a gradual but complete metamorphosis into a young conger. 

 The latter at the end of the transformation was 3^ in. long. 

 The Leptocephalus morrisii is from 4 to 5 \ in. or even 6 in. in 

 length, and during the metamorphosis a distinct reduction in 

 length takes place. The Leptocephalus is ribbon-shaped and 

 transparent, and has no red blood-corpuscles nor air-bladder. 

 The young conger has red blood-corpuscles, a round body, a 

 pigmented skin, a head of normal proportions, and a well- 

 developed air-bladder. 



In 1888, among a large number of pelagic marine fish eggs 

 from the Bay of Naples, the Italian naturalist Raffaele described 

 five different kinds of which he could not discover the parentage, 

 but which had a close resemblance to one another, and which 

 in his opinion probably belonged to fishes of the eel family. 

 This opinion was chiefly founded on the characters of the 

 larvae hatched from the eggs in question. These larvae were 

 of much elongated form with a large number of muscle segments. 

 Shortly after hatching they developed in the lower jaw peculiar 



