CNIDOSPORIDIA, ACTINOMYXIDIA 469 



develop in turn into 8 spores. Whether the pansporoblast is 

 formed by the union of 2 cells or not, is yet to be confirmed. The 

 nuclei and cytoplasm divide and isogamy takes place. The zygote 

 thus formed is the sporont, from which a single spore is produced 

 by repeated nuclear division combined with cytoplasmic differ- 

 entiation. 



The Actinomyxidia inhabit the body cavity or the gut-epithe- 

 lium of fresh or salt water annelids. 



Spore with a double membrane; inner membrane a single piece, the 

 outer trivalve; a single binucleate sporoplasm 

 Famil}^ 1 Tetractinomyxidae 



Spore membrance a single trivalve shell; a single octonucleate sporo- 

 plasm or 8 uninucleate sporoplasms 



Family 2 Triactinomyxidae 



Family 1 Tetractinomyxidae Poche 



Genus Tetractinomyxon Ikeda. In coelom of the sipunculid 

 Petalostoma minutum; spores tetrahedron, without processes; 

 trophozoite a rounded body, when mature; pansporoblast devel- 

 ops 8 spores. Seemingly borderline forms between the Myxo- 

 sporidia and the Actinomyxidia. 



T. intermedium I. (Fig. 217, a). Spherical pansporoblasts 20- 

 25ju in diameter; spores 7-8/x in diameter; in coelom of the sipun- 

 culid, Petalostoma minutum. 



Family 2 Triactinomyxidae 



Genus Triactinomyxon Stole. Each of 3 shell-valves drawn out 

 into a long process, the whole anchor-like; spore with 8 or more 

 uninucleate sporoplasms; in gut-epithelium of oligochaetes. 



T. ignotum S. (Fig. 217, d). Spore with 8 sporoplasms; in Tubi- 

 fex tuhifex. 



T. magnum Granata. Spore with 16 sporoplasms; in Limno- 

 drilus udekemianus. 



T. legeri Mackinnon et Adams. Spore with 24 sporoplasms; in 

 Tuhifex tuhifex. 



T. duhium G. Spore with 32 sporoplasms; in Tuhifex tuhifex. 



T. mrazeki M. et A. Spore with 50 sporoplasms; in Tuhifex 

 tuhifex. 



Genus Sphaeractinomyxon Caullery et Mesnil. In coelom of 

 oligochaetes; spores rounded, without any processes; in early 

 stage of development, there are 2 uninucleate bodies surrounded 



