530 GENERATION. [CHAP, xxxvi. 



and this process is repeated for nine or ten generations. The last 

 autumnal brood, however, of these larvae produce in the same vivi- 

 parous manner perfect male and perfect female insects, with fully- 

 developed sexual organs. The female deposits her ova in the axils 

 of the leaves and other protected parts of the plant, where they 

 remain till the following spring, when they are hatched, and the 

 larvae above-described issue forth : the first larva producing eight, 

 and each of these repeating the process, until, in the course of the 

 summer, millions of larval forms are produced. This must conclude 

 our very imperfect sketch of these interesting processes ; and, for 

 more detailed information, we must refer the reader to the works 

 enumerated at the end of the present chapter. 



Professor Owen considers, that the larval forms result from the 

 development of a portion of the original germ-substance of the 

 yolk, which was not converted into a portion of the textures of the 

 beings which resulted from the immediate development of the 

 ovum ; and hence he has applied the term parthenogenesis, or virgin 

 generation, to this process of development. Dr. Carpenter, on the 

 other hand, looks upon the process as akin to gemmation, or 

 budding, rather than one of actual generation. Victor Carus shows 

 that in this process of development the embryo is formed from a 

 granular germ, whereas ordinarily it results from the process of 

 cell-multiplication, as will be shown in the chapter on the develop- 

 ment of the embryo. The same author contrasts the process of 

 metamorphosis and metagenesis in the following words : " Larvae, 

 the subjects of metamorphosis, arrive at the state of perfection by 

 throwing off provisional structures which belong to their larval con- 

 dition; but nurses,* the subjects of metagenesis, are themselves 

 entirely provisional structures." 



In the present state of knowledge, it is difficult to group these 

 extraordinary phenomena under one general head. Although 

 we may contrast the processes of metamorphosis and metagenesis 

 with each other, and draw definite distinctions between them, we 

 must remember, that there are instances in which both these pro- 

 cesses occur ; and although metamorphosis affects a single indivi- 

 dual, and metagenesis a very numerous progeny, we do not feel 

 ourselves in a position to define the exact relation which one bears to 

 the other, and we think it better to avoid any attempt at generalisa- 



* The term " nurse" was originally applied by Steenstrap to these larval 

 forms ; but we have purposely avoided its use, as it is for many reasons very 

 objectionable, and likely to convey a wrong idea of the nature of the viviparous 

 larvae. 



