120 METAMOBPHOSES OF MAN 



processes ? Who does not see that these phenomena, 

 which are so curious even in the commencement, and 

 which in a general aspect are identical with those of 

 . vivipara, and are performed by an entirely similar 

 apparatus, are after all but transformations ? First, 

 epigenesis, and then simple or complex evolution. 

 These are the processes we see taking place in every 

 organ which is added to those of the larva, in con- 

 verting it into an insect, a crustacean, or a perfect 

 reptile. Formation is evident; and modification and 

 progressive development occur beneath our eyes, when 

 we see the external gills and the internal which 

 succeed them and precede the lung in the frog, the 

 dorsal projections which appear in the phlebenterate 

 mollusk, the wings which are pushed out from the 

 thorax of the insect, and the segments which are 

 added to those already existing in the myriapod. 



an absolute law, nor to associate the greater or lesser complication 

 of the metamorphoses, only with the greater or lesser volume of 

 vitellus. I merely wish to point out one cause which has not 

 been taken sufficiently into account, but which is doubtless only 

 one of a series. The period of incubation, for example, may also 

 be regarded as an important element in the inquiry, and as exerting 

 a decided influence. The egg of Hermella and of Teredo is in twelve 

 hours entirely transformed into an animal endowed with the power 

 of voluntary movement. This is, doubtless, another of the prin- 

 cipal causes of the extreme simplicity of the larva." I have since 

 become aware — through M. Claparede's work — that Leuckart had 

 attributed metamorphoses to the insufficiency of the plastic ele- 

 ments of the yolk, even before I had done so. I am glad to meet 

 on this point with a naturalist who has given us so many splendid 

 memoirs since that period. But, so far as I can see, I cannot 

 admit with him that it is the sole cause of metamorphoses. M. 

 Claparede has already maintained that this conclusion is too abso- 

 lute, and has, it seems to me, gone too far in the opposite direction. 

 — Bibliotheque Universelle de Geneve, I. c. 



