140 



THE RADIOLARIA 



minute crystals arise in the endoplasm, a few larger ones also in certain 

 Collosphaeridae. The single oil-globule of each capsule becomes 

 very rapidly subdivided into as many minute vesicles as there are 

 nuclei, and in association with this process a blue pigment develops 



XTV^f^ V^?7t-;} 



A. **>.. es& H, 



.?/ 



FIG. 23. 



Collosphaera huxleyi. Optical sections of different growth-stages to illustrate (A, B) diraor- 



Shism (Si, Sa) in early and later stages, and (C, D) the formation of isospores. A, yoiuig actively 

 ividing colony (the young reproductive phase of Brandt, comparable with the . formation of 

 extracapsular bodies in Sphaerozoidae). Many individuals are naked central capsules with 

 one or more nuclei; others have a shell (.Sj) and are larger and already provided with 

 zooxanthellae (z). B, later vegetative phase. The naked capsules have now secreted a large 

 shell (S 2 ), and a marked dimorphism has resulted. C, part of a full-grown*colony about to 

 sporulate. The formation of isospores is indicated by the grouping of the nuclei. D, later 

 stage in isospore- formation showing the crystals aggregated about the oil-globule. x 75. 

 (After Brandt.) 



jn Myxosphaera coerulea and Collosphaera hudeyi. Numerous vacuoles 

 arise in the centre of the capsule, each with a central granule, until 

 a number equivalent to that of the nuclei has been formed. Mean- 

 time these nuclei, which have become very numerous, are evenly 



