224 SOME MINUTE ANIMAL PARASITES 



original nuclei gives off a small bud-like nucleus, 

 which migrates to the polar capsule and there con- 

 trols its growth. This is known as the polar capsule 

 or capsulogenous nucleus. The remainder of the 

 second nucleus again divides into two, so that the 

 spore contains five nuclei. These last two nuclei 

 remain in the sporoplasm. 



It should be noted that these nuclei are not all of 

 the same size and shape, nor do they all persist for 

 the same length of time. When the sporocyst 

 nuclei have completed their work, they often gradu- 

 ally degenerate and disappear. The same occurs 

 with the polar capsule nucleus, and consequently 

 spores with less than five nuclei are found. 



While these nuclear divisions are occurring, the 

 sporocyst is becoming very thick and opaque, and 

 it is often necessary to use strong reagents such as 

 creosote to render them less opaque in order to see 

 the contents after staining. The five nuclei in the 

 spore are of much interest, for they represent an 

 attempt at division of labour in the structure of a 

 Protozoon. Until the sporocyst nuclei are formed, 

 the sporocyst develops but very little. It increases 

 rapidly after their formation. Similarly the develop- 

 ment of the polar filament proceeds apace only under 

 the controlling influence of the associated nucleus. 

 The two sporoplasmic nuclei control the activity of 

 the sporoplasm, which ultimately leaves the spore 

 and becomes the young amcebula with which the life- 

 history began. 



When the spores of Nosema rupture the cells in 

 which they are lodged, or the latter are set free into 



