568 MAYOR. 



distribution of the spores, both by retarding the rate at which they 

 sink and by rendering them more easily carried by currents. 



The polar capsules are almost spherical and lie close together at 

 the anterior end of the spore. They are so oriented that the polar 

 filaments when extruded cross each other (Fig. B, b). The extrusion 

 of the polar filaments was effected by the action of concentrated sul- 

 phuric acid, and by a solution of iodine in potassic iodide, but they 

 were not extruded by ammonia-water. The failure of the latter 

 reagent may have been due to the spores not having been ripe. When 

 extruded the filaments appear as very fine threads of uniform thick- 

 ness. 



The sporoplasm as seen in fixed and stained preparations is eccen- 

 trically placed (being nearly all in one valve), and contains, in all the 

 spores studied from the gall bladder, two compact darkly staining 

 nuclei (PI. II, Fig. 40). The dimensions of the spores are given under 

 the diagnosis of the species. 



3. Abnormalities in the Structure and Development of Spores. 



Triradiate spores of C. acadiensis were of frequent occurrence 

 in all tliree hosts of the parasite. These spores may show a fairly 

 regular radial symmetry, both as regards the valves and the polar 

 capsules (Fig. C, a), or one of the valves may be smaller than the other 

 two, while the three polar capsules are of equal size and symmetrically 

 arranged (Fig. C, b). 



Cases where a triradiate spore and a normal spore were developing 

 in the same myxosporidium were found (Fig. C, c), also cases where 

 two triradiate spores were developing together in one myxosporidium. 



The possession of a triradiate spore-shell formed from three cells 

 is characteristic of the group Actinomyxidae. The frequent occur- 

 rence of triradiate spores, whose shell is presumably formed by three 

 cells (since in many cases three polar-capsule nuclei can be seen), 

 is interesting as indicating a possible relationship between these two 

 groups. 



