460 



BIOLOGY OF THE PROTOZOA 



spines. Each spore has three polar capsules containing distinct 

 protriisible filaments. 



The development processes leading to the formation of spores 

 involves fertilization phenomena of a characteristic type. They are 

 essentially similar to those of the IMyxosporidia but differ in some 

 important details. A plasmodial stage appears to be absent or 

 represented by a binucleate amcebula only, which develops into a 

 spore. The two nuclei divide and form 4 cells, 2 of which disappear 

 with the formation of a membrane within which the other 2 cells 

 Each of these divides forming 4, 2 of which continue to divide 



lie. 



rapidly until S are formed while the other 2 remain large and 



Fig. 192. — Spores of Actinomyxida. A, H exact inomy. von psammoryctis, after 

 Stolg, B, SphdEractinomyxon stolsi; C, Triadinomyxon ignotum; D, same, spore bearing 

 part enlarged, after Leger; E, Synactinomyxon tubificis. (After Caullery and Mesnil.) 



undivided the two-celled membrane now containing 8 small and 

 2 large cells. Ultimately the 2 large nuclei begin to divide in 

 turn until 8 products result and 16 cells, regarded by Caullery 

 and Mesnil (1905) and by Ikeda (1912) as gametes, lie free in the 

 cyst. The two sets of gametes differ slightly in nuclear size and 

 in staining capacity and unite 2 by 2 to form 8 zygotes. The nucleus 

 of each zygote now divides until 6 small nuclei and 1 large one result, 

 the large one destined to form a mass of sporozoites. The 6 small 

 ones arrange themselves in such a manner as to form 3 shell-forming 

 cells, while 3 of them lie within and form 3 ])olar capsules. The 

 germ-forming cell is not enclosed by the spore-forming cells but lies 



