PHYLUM PROTOZOA 79 



RThe spores are often very complex ; in some cases (B) they possess organs 

 ke the trichocysts of Infusoria and the iiematocysts of Zoophytes (vide infra) ; 

 in others they have the form of curious twisted bodies called psorosperms, found 

 in the gills, kidneys, &c. , of fishes ; they have been seen to liberate amcebula?. 



ORDER 4. SARCOCYSTIDEA. 



The best known form of this order is Sarcocystis (Fig. 59), which occurs in the 

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



FIG. 59. Sarcocystis miescheri, adult form (s) in striped muscle of pig. (From 

 Blitschli's Protozoa, after Raiuey.) 



striped muscular fibre. They are often known as Ramey's or Miescher's 

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

 liberated. 



CLASS V, -INFUSORIA. 



1. EXAMPLE OF THE CLASS Paramcecium caudatum. 



Structure. Paramceciuwi, the " slipper-animalcule," is tolerably 

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

 60) is somewhat cylindrical, about J mm. in length, rounded at 

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

 ventral face is a large oblique depression, the luccal groom (hue. 

 gr.); leading into a short gullet (gul.), "which, as in Eugiena, 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/ (cort.) and 

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

 cuticle (cu.) continued down the gullet. The cilia are prolongations 

 of the cortex, and perforate the cuticle. 



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

 very characteristic. One, distinguished as the meganudcus (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 micronuclcus (pa. nu.\ 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). 



The contractile vacuoles (c. me.) 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 



