390 RUTH J. STOCKING 



animal divided eight times and its history was similar to that 

 given above for the experimentally produced abnormalities in 

 Paramecium. The abnormal character was handed on to one 

 cell at each division, and the abnormal annual produced by the 

 eighth division died. All of the sister cells and their progeny 

 were normal. The only other observation known to me on the 

 abnormalities arising after conjugation is made by Jennings in 

 his 1913 paper quoted above. While he found only extremely 

 rare and transitory abnormalities among his 'split pairs' and 

 'free' individuals, he found a large proportion of malformations 

 among his exconjugants and their progeny. He describes their 

 different types, characteristics, and constant and continued 

 appearance throughout the course of his experiments; and adds, 

 "A precise study is greatly needed, as to the minute character- 

 istics of these abnormalities, their heritability, their experi- 

 mental cause, and their cytological basis." It was at his sug- 

 gestion that a series of experiments was started for the purpose 

 of studying these problems, and under his direction that these 

 experiments have been carried through. I wish to express here 

 my most sincere thanks for the constant help he has given 

 during the entire course of the work. 



II. METHODS 



In all of the cultures on which this work is based the method 

 of handling, cultivating, and recording was identical with that 

 described by Jennings ('13). Conjugation was first induced; 

 after the pairs had separated the two members were isolated and 

 cultivated separately in xe per cent Horlick's malted milk 

 (Peebles, '12). Each pair was numbered, and the two members 

 of a pair designated a and b; the races which arose from these 

 exconjugants were called after them in the same way, 2a, 2h, 

 3a, and so on. Beside the slide cultures, mass cultures were 

 also kept for each race. These were kept in bottles and each 

 bottle was labelled correspondingly, 2a, 2b, 3a, and so on. The 

 method of recording described by Jennings was supplemented 

 in my work by drawings of the abnormal forms. In a few cases 



