314 ROBERT T. HANCE 



2. Conjugation appeared in cultures having a comparatively 

 small amount of fluid supporting a large number of paramoecia. 



3. No conjugations were seen in some cultures undergoing the 

 same treatment as 1 and 2 particularly when the concentration 

 was not rapid. 



4. No conjugation took place in cultures made up with a large 

 amount of fluid. 



5. When a slight amount of sea salt was present conjugation 

 sometimes occurred a little before the control of plain hay infu- 

 sion showed signs of this condition and in all cases the epi- 

 demic of conjugation in the saline solutions died out before it 

 did in the pure hay media. 



As a discussion of the various theories of conjugation in rela- 

 tion to the results given above is somewhat foreign to the main 

 subject of this paper a full consideration of the phenomena will 

 be published separately. 



VI. GENETICS 



The account that precedes this section has dealt with the 

 general beha\'ior and inheritance of the contractile vacuoles. 

 In this section will be considered the inheritance of the extra 

 organs for several consecutive generations and the effect of 

 selection and of conjugation on the race. 



While these experiments might have been carried on for more 

 generations the technical difficulties were so great as to make 

 further pursuance of this Ifne of investigation unpracticable. 

 In this part of the work the animals had to be examined with 

 the 4 mm. objective in many cases to be certain of the number 

 of vacuoles they possessed, and to do this the animals could be 

 allowed so little fluid to move in that many times I have lost 

 them through drying thereby breaking the continuous line of 

 succession. Indeed, dozens of experiments were started before 

 the results illustrated below were obtained. 



a. The inheritance of the contractile vacuoles for four generations 



Lines were started with one two, one three and one four- 

 vacuoled paramoecium. As rapidly as they divided the num- 



