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 



S, 



FIG. 23. 



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

 phism (Si, S'>) in early and later stages, and (C, D) the formation of isospores. A, young actively 

 dividing 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 (.S']) 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.) 



in Myxosphaera coerulea and Collosphaera huxleyi. 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 



