78 



THREE CRUISES OF THE " BLAKE 



BRYOZOA. 



Ill the study of no group is abundant material more necessary 

 than in that of the bryozoans. 



In the majority of animals, Ave are accustomed to look at dif- 



Fig. 323. — Crisia denti- 

 culata. |. 



Fig. 324. — Diastopora 

 repens. y. 



Fig'. .325. — Farciminaria 

 delicatissima. | . (Busk.) 



ferences due to growth as transitory, and we define species from 

 their full-grown stages ; but in the bryozoans the differences of 

 growth are persistent in the individuals of the 

 colony, while they may propagate at very dif- 

 ferent stages of the colonial development. It 



Fig-. 323 a. — Crisia denti- 

 culata. Magnified. (Siuitt. 



Fig-. .324 a. — Diastopora repens. 

 Magnified, (ymitt.) 



thus becomes most difficult, without a f idl ^ia- 325 a 



Farcimi- 

 naria delicatissiraa. 

 Magnified. (Busk.) 



knowledge of the entire development, to char- 

 acterize a species and assign it to its true 

 family or genus. Among the bryozoa, more than three quarters 



