7 6 



GENERAL BIOLOGY 



12. In a fresh mount containing a large number of indivi- 

 duals study the division of Paramoecium (or, if more abun- 

 dantly evidenced, use any other available infusorian). 

 Observe the division of both mega- and micro-nucleus, and 

 the subsequent division of the protoplasm. Observe the 

 fate of the oral groove. The different stages may often be 

 found simultaneously in different dividing individuals. 



The record of this study may well consist in : 



1. A diagram to illustrate the spiral course of swimming 

 of Paramoecium. 



2. A diagram to illustrate the movements by which an 

 obstruction is avoided. Indicate plainly oral and aboral 

 sides. 



3. A detailed drawing of a single animal, showing all its 

 normal structures. This should be begun with the begin- 

 ning of the study, and details added as they are worked out. 



4. A series of outline drawings illustrating the progress of 

 division. 



Study ii. 



The specialized cell-body of Stentor and 

 Vorticella. 



It will now be well to 

 study a few of the higher 

 protozoans, illustrating 

 the great degree of dif- 

 ferentiation of parts and 

 of specialization that 

 may occur in the single 

 free-living cell. For 

 this purpose two com- 

 mon protozoan inhabi- 

 tants of fresh water 

 ponds (fig. 53) are sel- 

 lected, Stentor and 

 Vorticalla. 



PIG. 53. Three common infusorians. A, 

 Paramoecium; n, nucleus; v, v, vacuoles; 

 /, food-ball at the bottom of the rudimen- 

 tary esophagus; p, peristome. C, Stentor; 

 I, lorica. F, Vor" " 

 contracted. 



Vorticella; s, extended; t. 



