BIPARENTAL INHERITANCE OF SIZE IN PARAMECIUM 



H. S. JENNINGS AND K. S. LASHLEY 



The Zoological Laboratory of The Johns Hopkins University 



In a recent paper ('13) we have shown that there is biparental 

 inheritance of the rate of fission in Paramecium — the two Hnes 

 of progeny descended from a pair of conjugants being more alike 

 in their rates of fission than would be the case if their parents 

 had not conjugated. The present paper examines the question 

 whether there is likewise biparental inheritance in size as a result 

 of conjugation. 



The material for this examination was derived from the exten- 

 sive Experiment 16, described in our previous paper. In this 

 experiment 482 lines of propagation, derived from the two mem- 

 bers, a and h, of 241 pairs, were cultivated side by side, under 

 uniform conditions, for forty-seven days. In addition to the 

 main slide cultures, employed for the study of the rate of fission, 

 there was kept a small mass culture of each line. These mass 

 cultures were likewise kept under uniform conditions; they fur- 

 nished for measurement large numbers of specimens of each line. 



On April 17, 1913, twenty-five days after conjugation, and 

 nineteen days after the mass cultures were set in progress, a con- 

 siderable number of specimens from each line were killed in 

 Worcester's fluid and preserved for measurement. Later, 2687 

 of these specimens were measured. Those measured belonged to 

 86 diverse lines, derived from 43 diverse pairs of conjugants; 

 thus on the average a trifle above 31 specimens were measured 

 from each of the 86 lines. The numbers measured varied, how- 

 ever, from 16 to 66 for given lines (table 3). 



It would of course have been of interest if descendants from a 

 larger number of pairs could have been included, but the details 

 of conducting so large an experiment as this one, concerned mainly 

 with the study of the rate of fission, are so laborious that we did 



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THE JOLRXAL OF EXPERIMENTAL ZOOLOGY, VOL. 15, NO. 2 



