D. PROTOZOA AND PROTOPHYTA. 



One-celled animals and plants in which the entire body consists 

 of a single cell, which may be independent or may be joined with 

 others to form a colony. 



I. PARAMEC1UM CAUDATUM. 



(A Ciliate Protozoon). 



A. MORPHOLOGY. 



Put a small drop of water containing Paramecia on a slide ; sur- 

 round it with gelatin to limit the movement of the animals, cover 

 and examine with the low power (of the microscope) and then with 

 the high power. Note : 



I. Size : measure. 



2 Shape: fusiform; rounded at the anterior end, bluntly pointed 

 at the posterior end. 



3. Locomotion : due to cilia uniformly distributed over the whole 

 surface. Xote also movements of flexion. 



4. Structure. The two layers: ectosarc (ectoplasm) and enclo- 

 sarc (endoplasm). 



a. Ectosarc (Cortex) : the firm elastic outer layer; its deeper 

 part marked by oblique myophan striations, probably due to longi- 

 tudinal wrinkling of the inner surface of the ectosarc. 



(i). The cuticle, a delicate superficial layer differentiated from 

 the underlying protoplasm. 



(2). Cilia, delicate vibratile filaments arising from the ectosarc 

 and protruding through openings in the cuticle. These openings can 

 be seen on a specimen from which the water is allowed to evaporate. 



(3). Trichocysts : minute oval sacs in deeper part of the ecto- 

 sarc arranged perpendicular to the surface ; when the animal is irri- 

 tated, e. g. by iodine, a stiff thread can be shot out and projected 

 beyond the cilia. They are probably defensive organs. 



(4). Two contractile vacuoles in the ectosarc of the dorsal side 

 about 1/3 of the animals' length from each end. \Yhile dilating they 

 are nearly spherical, but at the moment of contraction separate 

 canals can be seen radiating from them. 



(5). The buccal groove begins at the anterior end of the left 

 side and runs back to the mouth near the middle of the ventral 

 side. The cilia of the groove drive food particles into the mouth. 

 Run some Chinese ink in water under the cover glass and note that 

 some of it is carried into the groove. 



(6). The mouth is an aperture in the ectosarc at the posterior 



