78 



THREE CRUISES OF THE " BLAKE. 



BRYOZOA. 



In the study of no group is abundant material more necessary 

 than in that of the bryozoans. 



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



Fig. 323. Crisia denti- 



culata. |. 



Fig. 324. Diastopora 

 repens. ^. 



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- 

 culate Magnified. (Sniitt. ) 



Fig. 324 a. Diastopora repens. 

 Magnified. (Smitt. ) 



thus becomes most difficult, without a full Fi 3250. Farcimi- 



Magnified. (Busk.) 



knowledgre of the entire development, to char- 



j . ., ., 



acterize a species and assign it to its true 



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



