ii PHYLUM PROTOZOA ; 



The spores are often very complex ; in some cases (B) they posse- 

 like the trichocysts of Infusoria and the nematocysts of /oopli\ t.^ ,;,-;,, 

 in others they have the form of curious twisted bodies called psorospt //,. 

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



ORDER 4. SARCOCYSTIDEA. 



The best known form of this order is Sarcoryxfis (Fig. 59), which occurs in ti..- 

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



.-JiV 



"- 





FIG. 59. Sarcocystis miescheri. adult form (*) in striped muscle of pit: (From 

 Biitschlis Protozoa, after Kuiiiey.) 



striped muscular fibre. They are often known as Raimy's or J// .,/,, ,-\ 

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

 liberated. 



CLASS V.-INFUSORIA. 

 1. EXAMPLE OF THE CLASS Pammcecium tiaudatum. 



Structure. Pa.ramcecium, the " slipper-animalcule," is tolerablv 

 common in stagnant ponds, organic infusions, &c. The bodv(FiL; 

 60) 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 biiccal groove (buc. 

 gr.), leading into a short gullet (yul.), 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 vn-v 

 clearly differentiated into a comparatively dense cortc,'- (co/1.) and 

 a semi-fluid -nif<]nll (m<d.), 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 arc 

 very characteristic. One, distinguished as the meganudeui-^nu.), 

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

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

 The other, called the micronuclcus (pa. mi.), is a vt TV 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. vac.) are two in number, and arc very 

 readily made out. Each is connected with a series of radia tin-- 

 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 siiiToundin- 



