14 DERIVATION OF ORGANIC BEINGS. 



three stages, all of wliicli come out prominently in one form 

 or other of alternation, while, as I shall endeavour to show, 

 they are covertly represented even in those species in which 

 no phenomena of alternation are recognised. The first, or 

 what I term the protomorphic stage, is that which intervenes 

 between the fecundation of the germ and the first appearance 

 of the characteristic or typical organization of the species ; 

 the second, or ortkomorphic, that which corresponds to the 

 development and full perfection of this organization ; while 

 the third, or gamomorpJdc, is that of the formation or matu- 

 ration of those structures in w^hich the spermatic and germi- 

 nal elements are generated, in preparation for another act of 

 fecundation, as the commencement of a new genetic cycle. 



In one of the forms of alternation just noticed, the inter- 

 polation of gemmation takes place in the protomorphic 

 stage, — that is, prior to that development by which the 

 features most characteristic of the species are gTadually 

 evolved. The other form of alternation, just contrasted 

 with it, is that in which the process of gemmation is inter- 

 polated in the gamomorphic stage — ^that is, after the general 

 acquisition of the typical conformation of the species, and 

 in connection v/ith the development of the organs which 

 form the sexual elements. 



In the intermediate period of the life history of the 

 species — that here termed ortliomorpliic — which intervenes 

 between the appearance of the general typical character of 

 the family and the maturation of sexual organs, gemma- 

 tion, though, perhaps, a more frequent character than either 

 in the incipient or terminal stages, rarely comes before us 

 as a case of alternation of generations, in consequence of 

 the gemmae commonly remaining in adhesion to each other, 

 so that their separate individuaUty is never clearly mani- 

 fested, and the whole aggregation passes as a single plant or 

 animal. This is especially the characteristic an'angement 

 in the vegetable kingdom, and in the zooph}i:ic forms of 



