554 H. S. Jennings and George T. Hargitt. 



4. The fourth case (p. 149) relates to the isolation of a small 

 Stentor, whose progeny retained the small size. Again the orig- 

 inal culture is not stated to hav^e been derived from a single indi- 

 vidual, so that it may have contained races of different size. Again, 

 the author does not know the characteristics of the line of ances- 

 tors from which the small specimen came. There is thus no 

 evidence that the small race arose from one of a different size. 



The two remaining cases (5 and 6) are based on experimental 

 operations; they give better evidence than those we have con- 

 sidered. 



5. The fifth case (p. 153-154) was as follows: By centrifug- 

 ing a Stentor for five hours, it was caused to divide unequally, 

 the smaller part receiving three nodes of the nucleus, the larger 

 sixteen. This was on April 9. On April 11 both parts had grown a 

 new peristome. "From this moment on, fission took place reg- 

 ularly. Up to April 18, on which day the cultures came to an 

 end on account of unforeseen lack of food, the size at fission showed 

 no change. In this way two size-varieties of Stentor were pro- 

 duced, which retained further their (relative) sizes" (p. 154). 



This experiment would be demonstrative, save for the fact 

 that the cultures were kept only seven days after the normal 

 form was restored. In an earlier paper ('08a) I showed that in 

 Paramecium abnormal bodily conditions .are often handed on for 

 a number of generations, but that as a rule they are finally gotten 

 rid of, and the normal condition is restored. It is entirely pos- 

 sible that this would have occurred in the case of the abnormal 

 size of Stentor. Popoff does not tell us how many fissions took 

 place in the seven days; as the animals had recently been operated 

 on, fission was probably slow. It is not at all surprising that the 

 abnormal condition had not been fully regulated in this brief 

 period even though it might have been regulated later. The 

 experiment is not therefore a demonstrative one. 



6. The sixth and last case (p. 157-262) relates to a Stentor 

 which was isolated from a "room culture"; by subjecting this 

 animal to cold a fission that had begun was suppressed. Various 

 abnormalities and monstrosities resulted, but there finally ap- 

 peared from it a race of Stentors much larger than usual, with 



