II 



PHYLUM PROTOZOA 



75 



The spores (6, c), formed by the breaking up of the protoplasm of the parent escape 

 in a form very unlike the adult, the tentacle or large flagellum hem" repre 

 sented by a short thick process, while the main swimming organ of the ila-ullula 

 becomes the small oral flagellum of the adult. 



CLASS IV. SPOROZOA. 



1. EXAMPLE OF THE CLA.ssMonoeystis 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 vcsiculae seminales of the 

 common Earthworm. It is flattened, greatly elongated, point -d 

 at both ends, and performs slow movements of expansion and 



D 



Fio. 55. Monocystis agilis. A, B, two individuals in different stages of contraction : 

 C, cyst containing spores; DF, development of young (M) in a group of sperm-. < 11s 

 of the Earthworm ; G, newly liberated Monocystis surrounded by sperms of tin. 1 Karthwonn ; 

 ,!/, young Monocystis ; nu. nucleus ; sp. sperms or sperm-cells of Earthwoi in. (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.) \\itli 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 proces 

 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 



