. 



PHYLUM PROTOZOA 



75 



The spores (&, c), formed by the breaking up of the protoplasm of the parent, escape 

 a form very unlike the adult, the tentacle or large flagellum being repre- 

 jnted by a short thick process, while the main swimming organ of the flagellula 

 monies the small oral flagellum of the adult. 



CLASS IV, SPOKOZOA, 



1. EXAMPLE OF THE CLASS Monocystis agilis. 



One of the most readily procured Sporozoa is the microscopic 

 worm-like Monocystis agilis (Fig. 55, A, B), which is commonly 

 found leading a parasitic life in the vesiculee seminales of the 

 common Earthworm. It is flattened, greatly elongated, pointed 

 at both ends, and performs slow movements of expansion and 





C 



FIG. 55. Monocystis agilis. A, B, two individuals in different stages of contraction; 

 C, cyst containing spores ; D F, development of young (M) in a group of sperm-cells 

 of the Earthworm ; G, newly liberated Monocystis surrounded by sperms of the Earthworm ; 

 M, young Monocystis ; nu. nucleus ; sp. sperms or sperm-cells of Earthworm. (After Biitschli 

 and Huxley.) 



contraction, reminding us of those of Euglena. The protoplasmic 

 body is covered with a firm cuticle, and is distinctly divided into 

 a denser superficial portion, the cortex, and a central semi-fluid 

 mass, the medulla. There is a large clear nucleus (nu.) with a 

 distinct nucleolus and nuclear membrane, but the other organs of 

 the protozoan cell-body are absent : there is no trace of contractile 

 vacuole, of flagella or pseudopods, of mouth or gullet. Nutrition 

 is effected entirely by absorption. 



Reproduction takes place by a peculiar and characteristic process 

 of spore-formation. Either a single individual, or two individuals 

 closely applied together but not actually fused, become encysted. 

 Multiple fission then takes place (C), the protoplasm becoming 

 divided into an immense number of spindle-shaped spores, each 

 surrounded with a strong chitinoid coat, and thus differing 





