Evidence from Protozoans 



379 



points out, skeletal production is no mere matter of simple secre- 

 tion, or still less of crystallization, but of genuine organic growth, 

 as a detailed study of the completed structure and histogenesis 

 of the parts shows ; and by the further fact that the parts con- 

 cerned present characteristic differences for the different species. 

 Thus in the genus Aiilosphaera to which belongs the species we 

 have taken as an example, Haeckel recognized twenty-one spe- 



---a>sp. 



--c.ca-p. 



rt. 



FIGUUE 25. AULACAXTHA (aFTER BORGERt). 



as'p., astropyle. c.cap., central capsule. 



c 



n., nucleus. 



cies. Hacker re-examined about a third of these and added four 

 new ones. And the specific distinctions are furnished largely 

 in skeletal details. 



(f ) Openings in the Central Capsule of the Radiolaria 



, * 



Along with these facts of skeletal development may be 

 considered the development of the openings of the central 



