THE HELIOZOA 



Sexual (karyogamic) processes have only been observed in 

 Actinophrys and in Actinosphaerium ; the process in Actinophrys 

 has already been described ; the phenomena observed in Actino- 





Actinosphaerium. A, a mother-cyst just before it breaks up into primary cysts. The 

 nuclei are considerably reduced in number and the protoplasm contains numerous small 

 oval yolk-plates, y.p. B, the primary cysts have each divided into two secondary cysts. The 

 sister-cyst of a is not seen in the figure. N, nuclei ; c.m, mother-cyst membrane ; c.m%, cyst 

 membrane of the first order. (After Brauer.) 



sphaerium are in many ways remarkably different. The first indica- 

 tion of approaching karyogamy is the encystment of a single 

 individual. The pseudopodia are withdrawn, their axial filaments 



