152 



THE PROTOZOA 



about either by the simple rupture of the wall or by the swelling of 

 the central mass of useless material. The spores are thus freed, but 

 not the sporozoites; the latter are still confined within their double 

 walls, and cannot be liberated until they are swallowed by some host, 

 where, in the digestive tract, the two coatings are dissolved off by the 

 digestive fluids, and the sporozoites emerge in the form of minute 

 elliptical bits of protoplasm, each containing a nucleus. 



D E f 



Fig. 84. — Scheme of speculation in gregarinida. 

 A. Union of two individuals in a common cyst. B and C. The formation of gametes of similar 

 size. D. Union of the amoeboid gametes. E and F. Formation of sporozoites in the fused 

 gametes. 



The process of spore-formation in the many-chambered Gregarinida 

 is more complicated. Thus in Clepsidrina, a frequent parasite of 

 insects, the organism when mature throws off the epimerite by which 

 it is attached to an epithelial cell of its own host and, as a sporont, 

 secretes its cysts and undergoes nuclear division as in Monocystis. 

 The encysted animal, however, is carried to the exterior with the 

 fasces of the host, and sporulation is outside of the host or exogenous, 

 as opposed to the endogenous sporulation of Monocystis. In these 

 excreted cysts, according to Schneider ('75) and Biitschli ('84), the 

 archispores, instead of, as in RIonocystis, forming a peripheral layer 



