CNIDOSPORIDIA, ACTINOMYXIDIA 661 



are plainly visible m vivo. One to many sporoplasms occur in each 

 spore. In the fully grown stage, the body is covered by a membrane 

 and contains eight sporoblasts which develop in turn into eight 

 spores. Whether the pansporoblast is formed by union of two cells 

 or not, is unknown. The nuclei and cytoplasm divide and isogamy 

 takes place. The zygote thus formed is the sporont in which a single 

 spore is produced by repeated nuclear division combined with cyto- 

 plasmic differentiation. 



The Actinomyxidia inhabit the body cavity or the gut-epithelium 

 of fresh or salt water annelids. Taxonomy, morphology and develop- 

 ment (Granata, 1925). 



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



trivalve; a single binucleate sporoplasm 



Family 1 Tetractinomyxidae 



Spore membrane a single trivalve shell; a single octonucleate sporoplasm 

 or 8 uninucleate sporoplasms Family 2 Triactinomyxidae 



Family 1 Tetractinomyxidae Poche 



Genus Tetractinomyxon Ikeda. In the coelom of the sipunculid Pe- 

 talostoma minutum; spores tetrahedron, without processes; tropho- 

 zoite a rounded body, when mature; pansporoblast develops 8 

 spores. Seemingly borderline forms between the Myxosporidia and 

 the Actinomyxidia. 



T. intermedium I. (Fig. 286, a). Spherical pansporoblasts 20-25ju 

 in diameter; spores 7-8ju in diameter; in coelom of the sipunculid, 

 Petalostoma minutum (Ikeda, 1912). 



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 the gut-epithelium of oligochaetes. 



T. ignotum S. (Fig. 286, d). Spore with 8 sporoplasms; in Tubifex 

 tubifex. 



T. magnum Granata. Spore with 16 sporoplasms; in Limnodrilus 

 udekemianus. 



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

 Tubifex tubifex. 



T. dubium Granata. Spore with 32 sporoplasms; in Tubifex tubifex. 



T. mrazeki Mackinnon and Adams. Spore with 50 sporoplasms; in 

 Tubifex tubifex. 



Genus Sphaeractiroryxon Caullery and Mesnil. In the crelcm cf 

 oligochaetes; spores rounded, without any processes; in early stage 



