470 THE AMERICAN NATURALIST [Vol. LVI 



A study of the data set forth in the diagrams will show that 

 there is practically no modification of any line springing from 

 a Difflugia, after the supposed conjugation, in the direction of 

 the characters of the line founded by the other member of the 

 pair before the union. Any slight changes seeming to show 

 such modification are offset by just as marked variations away 

 from that line. Comparing line g with h, it would seem that 

 there is a marked modification of g in tlie direction of line e. 

 It must be noted, however, tliat line h consists of only 7 indi- 

 viduals, so that the average is untrustworthy. In no other case 

 is there any significant leaning toward the otlier line, although 

 there are very slight tendencies in that way in the spine num- 

 bers in experiment A. Line a has 2.7'J spines, h 2.85, c 4.05 

 and d 4.22. On the other hand, in experiment B the spine num- 

 ber in line e is 3.58 and in / only 2.12, to be compared with 4 

 in line h. It would be expected that line / would show a greater 

 number of spines than line e. In experiment C line k shows a 

 slight increase in spine number instead of the expected de- 

 crease. In general there are no apparent modifications of the 

 offspring as the result of the pairing. 



The experiments are open, of course, to the criticism that 

 the attachment between the Difthmias was brought about by 

 keeping the individuals iti distiHcd water to bring them to the 

 state of partial starvatidii which scciiis usually to be the fore- 

 runner of conjngation in the Piv.tozoa. It is possible that under 

 these somewhat unnatural conditions, the preliminary steps 

 incident to conjugation would be inaugurated but that the 

 process would stop before completion. In answer to this, T can 

 only state that tlie Diflingias remained attached from 12 to 24 

 hours, thus allowing sufficient time for nuclear changes to have 

 occurred. They became separated only wlien placed in cultures 

 containing food. 



To summarize then, as far as it is safe to base conclusions 

 on the results of this limited number of experiments, it seems 

 that the offspring of the DifHugias were not influenced by the 

 attachment or so-called conjugation of tlie ])a rents. From this 



E. P. Churchill, Jb. 



University of South Dakota 



