5?'. MANUAL: OF ZOOLOGY. 



poda\ and the Infusoria-.. In >the Infusoria only is a mouth 

 present, and hence these are .sometimes spoken of as the 

 " Stomatode" Protozoa, whilst the two former classes collec- 

 tively constitute \he"Asto?hata" 



The following is a tabular view of the divisions of the 

 Protozoa : 



Class I. GREGARINIDA. 

 Glass II. RHIZOPODA. 



Order i. Monera. 

 2. Amo&bta. 

 3. Foraminifera. 

 4. Radiolaria^ 

 5. Spongida.\ 



Class III. INFUSORIA. 



Order i. Suctoria. 

 . 2. Ciliata^ 

 3. Flagellat^ 



3. CLASS I. GREGARINIDA. The Gregarinida may be de- 

 fined as parasitic Protozoa, which are destitute of a mouth, and 

 do not possess the power of emitting " pseudopodia" They con^ 

 stitute the lowest class of the Protozoa, and comprise certain 

 microscopic animals which are parasitic in the alimentary canal 

 of both Invertebrate and Vertebrate animals. They have, 

 however, a special liking for the intestines of certain insects, 

 being commonly found abundantly in the cockroach. As 

 we shall see hereafter, in all probability a great deal of the 

 degraded character of the Gregarinida is due to the fact that 

 they are internal parasites, and are therefore not dependent 

 upon their own exertions for food. 



Nothing anatomically could be more simple than the struc- 

 ture of a Gregarina, since it is almost exactly that of a cell, 

 such as the impregnated ovum (fig. 6, b). An adult Gregarina, 

 in fact, may be said to be a single cell, consisting of an ill-de- 

 fined membranous envelope filled with a more or less granular 

 sarcode with fatty particles, and sometimes differentiated into 

 a distinct contractile " cortical layer," which contains in its in- 

 terior a vesicular nucleus, this in turn enclosing a solid particle, 

 or nueleolus. In some the body exhibits an approach to a more 

 complex structure by the presence of internal septa ; but it is 

 doubtful whether this appearance may not be due to the appo- 

 sition and fusion of two separate individuals. A separate order, 



