CNIDOSPORIDIA, ACTINOMYXIDIA 531 



H. mictospora Kudo. In the urinary bladder of Lepomis spp. and 

 Micropterus salmoides; spores 13.5-15)U long, 8-9m wide, 6-7. 5^ 

 thick; caudal prolongation 30-40m long. 



Order 2 Actinom3rxidia Stole 



The Cnidosporodia placed in this order have been less frequently 

 studied and, therefore, not so well known as the Myxosporidia. The 

 spore is enveloped by a membrane, or shell composed of 3 valves 

 which are sometimes drawn out into simple or bifurcated processes. 

 There are also 3 polar capsules in the spore and the polar filaments 

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

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

 and contains always 8 sporoplasts which 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 in 

 which a single spore is produced by repeated nuclear division com- 

 bined with cytoplasmic differentiation. 



The Actinomyxidia inhabit the body cavity or the gut-epithehum 

 of fresh or salt water annelids. 



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



tri valve; 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 Pt- 

 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. 254, a). Spherical pansporoblasts 20-25/x 

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

 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 the gut-epithelium of oligochaetes. 



T. ignotum S. (Fig. 254, d). Spore with 8 sporoplasms; in Tuhifex 

 tubifex. 



