SIZE RELATIONSHIPS BETWEEN CONJUGANTS AND 

 NON-CONJUGANTS IN BLEPHARISMA UNDULANS. 



FLORENCE A. WAITERS. 



It has been shown by Pearl ('07) that in Paramcecium cultures 

 the conjugants differ from the non-conjugants in size and varia- 

 bility and that a correlation in size occurs between the two 

 members of conjugating pairs. He has shown by statistical 

 methods (i) that the conjugants are less variable in size than 

 the non-conjugants, (2) that the conjugants show a smaller mean 

 size than the non-conjugants, and (3) that a marked correlation 

 in size exists between the members of the conjugating pairs, the 

 smaller uniting with the smaller and the larger with the larger. 



Jennings ('n) took up the problem of size relationships in 

 Paramoscium going into discussion of the reasons for the condi- 

 tions found, which he based on very careful observations of the 

 conditions existing in his cultures. After careful measurement of 

 a great many individuals he confirmed the results obtained by 

 Pearl, i. e., (i) that the conjugants are smaller than the non- 

 conjugating population of a culture; (2) that they are less 

 variable than the non-conjugants; and (3) that there is a marked 

 correlation in size between the members of the pairs, so that on 

 the whole larger individuals are found mated with larger, smaller 

 individuals with smaller. It was with the idea of investigating 

 the size relationships in another related form, that the present 

 work on Blepharisma undulans was taken up. It will be possible 

 here to give the facts of the size relationships only as they were 

 found in material already mounted. 



The individuals under consideration are from a pure-line culture 

 isolated at Woods Hole on July 20, 1911, by Professor Calkins. 

 The six lots with which I shall deal were killed by him at various 

 times during October, 1911, by means of sublimate acetic, 

 stained with Hoyer's picrocarmine, and mounted permanently 

 in Canada balsam. 



In measuring the individuals, a Leitz projectoscope was used 



