31-2 



PARASITES OF THE DOMESTIC ANIMALS 



imu'li Kii'iitiM' s|i('cializatinn in some tliaii in othoiy. While a nucleus is 

 not easily deinonstiahle in cci-tain of the Piotozua, most have one or 

 more (listinet nuclei, in this, as in other i-espects, jiossessina; the essential 

 parts of a typical cell, 



Ameba. — A simple representative of the Protozoa is the Amelia 

 (P^ia;. I(j8,) which may lie found in most any still water, most I'eadily in 

 the ooze upon the liottom oi- adhei'ino- to leaves or othei' submerged 



Fig. 108. — Ameba protcu.s (after CVawle^'. from Doflein; C'ir. 

 No. 194, Bureau An. Ind., U. S. Dept. Agr.). 



objects. Search of such material under the low power of the microscope 

 will reveal this oroanism as a minute protoplasmic particle which slowlj' 

 changes its shape and location by a peculiar flowing and extension of 

 the cytoplasm at one or more points, forming irregular, often finger-like, 

 projections, — the ]:)seudopodia. These may be withdrawn or the whole 

 substance of the animal may appear to flow into one of the pi'ojections; 

 by this manner of locomotion it may slowly pass out of the microscopic 

 field, (.'lose study of the oi'ganism will reveal two distinct regions, an 

 outer hyaline, — the ectoplasm (ectosarc), and a central more granular 

 and less transparent part, — the endoplasm (endosarc). Within the latter 

 may be seen the food vacuoles which ai-e rounded or oval, of varying 



