DERIVATION OF ORGANIC BEINGS. 13 



longing to the species, is still defective in having no proper 

 organs of reproduction — a function which is vicariously 

 performed by a set of gemmae detached from it. The 

 original stock is really neuter ; but true sexes appear in 

 these buds, after they have been transformed by a process 

 of development into isolated zooids or phytoids. They 

 may then be considered as a highly individualized form of 

 those organs which were wanting in the parent stock. Such 

 organs constitute, at least, the essential part of their 

 economy ; and although, along with them, there may be 

 present also others, more or less fully developed, for dis- 

 charging functions, such as alimentation and locomotion, 

 required by their status as free zooids, yet their gTeat office 

 is reproduction, and this end effected, their life speedily 

 comes to a close. In this they contrast strikingly with the 

 stock from which they were derived ; for it is endowed with 

 a much gxeater permanence of life, frequently detaching, 

 during its period of vigour, many successive swarms of 

 sexual zooids ; just as among the higher animals, the same 

 parent may develope many successive broods of young. 



On the other hand, when the budding process occurs in 

 the course of development, the gemmae are detached from 

 the immediate product of impregnation while it is still in a 

 rudimentary condition, comparable to the first stage in the 

 evolution of the ovum of the higher animals. The germ- 

 parent itself never attains to the full development of the 

 species, but remains the whole term of its brief existence in 

 a rudimentary state ; but the progeny, which it buds off, 

 acquire, in due course, the typical form, or at least give 

 origin, mediately or immediately, to others which do so. 



For the better distinction of these varieties of alternation, 

 and for the purpose of bringing out more clearly what I 

 ctjnceive to be their points of correspondence ^vith pheno- 

 mena occurring in the higher animals, I have found it con- 

 venient to divide the life history of an organic being into 



