68 PROTOZOA 



conjugation produce the microsplieric young. The microspheric 

 forms early become nmltinucleate, and have also numerous 

 chromidia detached from the nuclei, whicli they ultimately replace. 

 These collect in the outer part of tlie shell and aggregate into new 

 nuclei, around which the cytoplasm concentrates, to separate 

 into as many amoeboid young " pseudopodiospores " as there are 

 nuclei. These escape from the shell or are liberated by its 



Fig. 16. — 1, OrbuJina miiversa. Hiijlily inafriiitierl. 2, Glohigerina hulloides. Highly 

 magnified. (From Wyville Thomson, after d'Orbigny.) 



disintegration, and invest themselves with a shell to form the 

 initial large central chamber or megalosphere. 



In the ordinary life of the megalospheric form the greater 

 part of the chromatic matter is aggregated into a nucleus, some 

 still remaining diffused. At the end of growth the nucleus itself 

 disintegrates, and the chromidia concentrate into a number of 

 small vesicular nuclei, each of which appropriates to itself a 

 small surrounding zone of thick plasm and then divides by 

 mitosis twice ; and tlie 4-nucleate cells so formed are resolved 

 into as man V 1 -nucleate, 2-flagellate swarmers, which. conjuo;ate 



