CNIDOSPORIDIA, MYXOSPORIDIA, ACTINOMYXIDIA 313 



gills of Lucius and Perca. Cyst formation. The total length of 

 the spore 35 to 40 microns. 



Henneguya mictospora Kudo (Fig. 133, l-n). In the urinary 

 bladder of species of Lepomis and Micropterus salmoides. The 

 spore measures 13.5 to 15 microns long, 8 to 9 microns broad, 

 and 6 to 7.5 microns thick; caudel prolongation 30 to 40 microns 

 long. 



ORDER 2 ACTINOMYXIDIA STOLC 



The Cnidosporidia placed in this order have been less 

 frequently studied and, therefore, not so well known as the My- 

 xosporidia. The spore is enveloped by a membrane, or shell, 

 composed of three valves which are sometimes drawn out into 

 simple or bifurcated processes. There are also three polar cap- 

 sules in the spore and the polar filaments are plainly visible in 

 vivo. Several sporoplasms occur as a rule in each spore. In the 

 fully grown stage, the body is covered by a membrane and con- 

 tains always eight sporoplasts which develop in turn into eight 

 spores. Whether the pansporoblast is formed by the union of 

 two cells or not, is yet to be confirmed. The nuclei and cyto- 

 plasm divide and isogamy takes place. The zygote thus formed 

 is the sporont, from which a single spore is produced by re- 

 peated nuclear division combined with cytoplasmic differenti- 

 ation. 



The Actinomyxidia are parasitic in the body cavity or the 

 gut-epithelium of fresh or salt water annelids. 



The order is divided into two families as follows: 



The spore with a double membrane; inner membrane a single piece and 

 the outer trivalve. A single binucleate sporoplasm. Probably 

 border-line forms between the Myxosporidia and the present 

 order Family 1 Tetractinomyxidae 



The spore membrane is a single trivalve shell. A single octonucleate 



sporoplasm or at least eight uninucleate sporoplasms 



Family 2 Triactinomyxidae 



Family 1 Tetractinomyxidae 

 Genus Tetractinomyxon Ikeda. Parasitic in the coelom of 

 the sipunculid, Petalostoma minutum. The spore is tetrahedron 

 in form and does not possess any processes. When the tropho- 

 zoite reaches maturity, it is a rounded body, the pansporoblast, 

 in which eight spores are developed. 



