256 HlGfi SCHOOL ZOOLOGY. 



plasm being separated off by a special " central capsule " from 

 the ectoplasm. In the latter there are often found minute yel- 

 low Algfe, which appear to live " symbiotically" with the Ra- 

 diolaiia. 



17. The Sporozoa are distinguished frc m the Rhizopoda not 

 only by the absence of pseudo])odia,but by the presence of a well- 

 marked cuticle which limits the contractions of the protoplasm ; 

 they reproduce by spores, formed by the simultaneous division 

 of the plasma of an encyste<i individual into a Uiultitude of glo- 

 bular bodies, which eventually acquire characteristically-shai.cd 

 shells (Fig. 189,7,8). They are all parasi*.ic. some of them leing 

 intestinal parasites of the Invertebrates {Gregarinidce), others, 

 so-called cell-parasites, which multii>ly in epithelial or blood-cells 

 of both lower and higher animals, and others, finally, ectopara- 

 sites of fish, being found on the gill-filaments. The spores of 

 the last forms have singular lasso-like organs of attachment 

 (Fig. 189,„.) 



18. The name Infusoria ("occuiriug in infusions "—an indi- 

 cation of the saprophytic life of many of the forms — ) often 

 employed for the two remaining classes, was at one time used 

 to cover a host of microscopic creatures, to many of winch, such 

 as the Rotifers, we have already given some attention ; it is 

 now restricted to the higher Protozoa, and frequently to those 

 which are ciliated, the class name Mastigophora being reserved 

 for those which have flagella. As they undoubtedly include 

 the simplest forms, which touch both upon the Sarcodina and 

 the Vegetable Kingdom, they may be mentioned first. 



19. Many of the most minute animals belong to the flagellate 

 Infusoria (Fig. 19 'J), various monads — e.g., Nonas termo — hardly 

 reaching 1 -2000th of an inch in length. Such a form presents 

 definite specific characters, however, and retains a definite shape. 

 There can hardly be said to be a mouth ; rather there is a 

 vacuole at the base of the flagellum, which takes up food- 



