

HYDROZOA. 77 



the distinction of four kinds of individuality in 

 the animal kingdom. First, hereditary indi- 



2 

 N 



viduality, when from a single egg a single inde- 

 1 { pendent being is produced. Secondly, derivative 



i or consecutive individuality, or "that kind of 



Undj, independence resulting from an individualisation 

 ti of parts of the product of a single egg ; " as in 



many Lucernaridce, Corynidce, and Campanu- 

 tjj lariadcB. Thirdly, secondary individuality, where 



the product of one egg multiplies by continuous 

 gemmation, giving rise to an immoveable com- 

 munity ; as in the Sertulariadce. Lastly, there is 

 complex individuality, where a similar but move- 

 able community is formed ; as seen in the Caly- 

 cophoridw and Physophoridce. In this case, he 

 adds, " the individuals of the community are not 

 only connected together, but, under given cir- 

 cumstances, they act together as if they were one 

 individual, while at the same time each individual 

 1 may perform acts of its own." 



Others were for regarding the gonophores of the 

 fixed Hydrozoa as the perfect or adult stages of 

 the forms by which they were produced, the whole 

 j« process being viewed as one of ordinary meta- 

 morphosis. The particular objection just stated 

 e - applies also to the opinion under consideration, 



lT p : which has, nevertheless, found its advocates in a 



few writers of distinction. There is, no doubt, 

 • or , some degree of plausibility in a view which consi- 



in ders tne fixed Corynid or Campanularid as the 



U I 



1 







ia- 



- 





-j 



Medusoid 



which, by gemmation, it gives rise. It is now, 

 however, certain not only that the Calycophoridce 

 and ffiysophondce agree closely in structure with 

 the Hydrozoa just named, hut liVpwiQA tw. fW 



