o/" Me Echinoderms. 15 



Individuality has so long and so obnously, among the higher 

 animals, been obsencd to be accompanied by independent exist- 

 ence, that the latter attribute has come to be considered as, con- 

 versely, an indication of individuality — to the neglect of the really 

 characteristic attribute, which is — the circumstance of being the 

 total result of the development of a single ovum. 



According to our view, then, the zoological individual = the total 

 result of the development of a single ovum, whether this total 

 result consist of one or many independent existences. The in- 

 dividual is the zoological unit, and its value is the same, whether 

 we have it as (1) or as (l^ + y + y)- A fraction does not become 

 equal to the unit by standing alone. The Cyansea and the Polype 

 from which it ])roceeds, the two forms of Salpse, the parent 

 nurses, nurses, and Cercari?e, of the Distomata, ai'e not distinct 

 individuals — are not separately equivalent to an indi\idual beetle 

 or dog. 



It is their sum only, which is equivalent to the indindual 

 among the higher animals. 



They are not the individual, but are successive forms by which 

 the in(lividual is manifested ; standing in the same relation to the 

 individual, as the incarnations of Vishnu to Vishnu, in the Hindoo 

 theology. 



What then may these independently existing " parts of indi- 

 viduals " be properly termed ? They can hardly be called organs, 

 without doing violence to our ordinary' acceptation of the nature 

 of an organ, in which a certain subserviency and dependence is 

 understood. The term " zooid" has been devised; and as it has 

 no theoretical meaning, but is merely intended to suggest two 

 indisputable facts with regard to the creatui'cs to which it is ap- 

 plied — namely that they are like indiWduals, and yet arc not in- 

 dividuals, in the sense that one of the higher animals is an indi- 

 vidual — its use does not appear to be open to any serious ob- 

 jection. 



Instead of saNang then, that in a given species, there is an 

 alternation of so many generations, we should say that the indi- 

 vidual consists of so many zooids. 



Again, where no "alternation" takes place, the individual = the 

 sum of its organs ; where there is alternation, the individual = 

 the sum of its " zooids." 



If the view we have taken be correct, the whole doctrine of the 

 so-called " compound animals " must be revised, and their termi- 

 nology altered. A whole tree of Sertularia, a Pennatula, a Py- 

 rosoma, a mass of Botrylli, must no longer be considered as an 

 aggregation of indinduals, but as an individual developed into 

 many zooids. 



And if the term " compound animal " is to be retained in its 



