88 ZOOLOGY sect. 



Order 5.— Sarcocystidea. 



The best known form of this order is Sarcocysiis (Fig. 68), which occurs in 

 the flesh of mammals, each parasite having the form of a long spindle embedded 



Fig. 68. — Sarcocystis miescheri, adult form (s) in striped muscle of pig. (From 

 Biitschli's Protozoa, after Rainey.) 



in a striped muscular fibre. They are often known as Rainey's or Mieschtr's 

 corpuscles. The protoplasm divides into spores from which falciform young are 

 liberated. 



CLASS V.— INFUSORIA. 



1. Example of the Class — Paramcecium caudatum. 



Structure. — Paramcecium, the "slipper-animalcule," is tolerably 

 common in stagnant ponds, organic infusions, &c. The body 

 (Fig. 69) is somewhat cylindrical, about \ mm. in length, rounded 

 at the anterior and bluntly pointed at the posterior end. On the 

 ventral face is a large oblique depression, the buccal groove (hue. gr.), 

 leading into a short gullet (gul.), which, as in Euglena, ends in the 

 soft internal protoplasm. 



The body is covered with small cilia arranged in longitudinal 

 rows and continued down the gullet. The protoplasm is very 

 clearly differentiated into a comparatively dense cortex (port.) and 

 a semi-fluid medulla (med.), and is covered externally by a thin 

 pellicle or cuticle (pu.) which is continued down the gullet. The 

 cilia are continuous with the pellicle. 



In the cortex are found two nuclei, the relations of which are 

 very characteristic. One, distinguished as the meganucleus (nu.), 

 'is a large ovoid body staining evenly with aniline dyes, which, 

 when it divides, does so directly by a simple process of constriction. 

 The other, called the micronucleus (pa. nit,), is a very small body 

 closely applied to the meganucleus; when it divides it goes 

 through the complex series of stages characteristic of mitosis 

 (p. 16).. m 



The contractile vacuoles (c. vac.) are two in number, and are very 

 readily made out. Each is connected with a series of radiating 

 spindle-shaped cavities in the protoplasm which serve as feeders 

 to it. After the contraction of the vacuole these cavities are seen 

 gradually to fill, apparently receiving water from the surrounding 



