igos.l. JENNINGS— HEREDITY IN PROTOZOA. 475 



results, the fact that a definite coefficient of variation cannot be con- 

 sidered characteristic of a given species or race. The observed 

 variation depends on many factors. 



Conjugating Culture. — The progen}^ of c I divided into two sets, 

 both of which were kept in larger culture vessels and maintained by 

 adding boiled hay at intervals. September 25 one of these cultures 

 was found to be undergoing an epidemic of conjugation (though, of 

 course, all were progeny of a single individual). The details regard- 

 ing the relation of conjugation to the phenomena we are studying are 

 to be taken up in a later communication, but I will give here the 

 essential facts regarding dimensions and constants of variation, in 

 order that our picture of the changes undergone by the c line may be 

 as complete as possible. A random sample of the non-con jugants 

 of this conjugating culture gave the results shown in row 21, Table 

 XVIII., and in Table LVII. The mean length (158.800 microns) 

 was considerably greater than has been observed in any other culture 

 of c. Whether this fact has any relation to the occurrence of conju- 

 gation, or whether it is merely a matter of the environmental condi- 

 tions must remain for the present a question. 



Scarcity of Food After Conjugation. — This conjugating culture 

 was allowed to stand five days. All conjugation ceased and the food 

 began to get scarce. Xow a sample gave the results shown in row 

 22, Table XVIII. , and in Table LVIII. The length had decreased 

 from 158.800 to 129.640 microns. Breadth likewise decreased, though 

 not in so great a proportion as length, so that the ratio of breadth to 

 length increased. As is usual when this ratio increases, the coeffi- 

 cient of correlation likewise increased. 



J^ariatiou in Different Divisions of the Same Pure Line on the 

 Same Date. — After the observations just described, the two cultures 

 composed of the progeny of c were maintained for several months. 

 On January 23, 1908, samples from each were measured, giving the 

 results shown in rows 23 and 25, Table XVIII. As is evident, the 

 two dift'ered considerably. The details do not demand attention, 

 save that in one of these old cultures (row 23, and Table LIX.) the 

 coefficient of correlation between length and breadth was the highest 

 I have ever observed in Paramecium, reaching .8500. Both these 

 cultures were flourishing and well fed. 



