lofi On the Genetics of the Ciliate Protozoa 



larger or smaller individuals. Popoff believes that ho has actually 

 observed this in Stentor and Frontonia (1909) and Stylonijchia (1908). 

 As a result of unequal division, large and small races arose. They both 

 had a normal karyoplasmic ratio, but differed in size. (See Fig. 5, 

 which shows the relative sizes of a large (A) and small (B) race of 

 Htentor — the animals being outlined at the moment of division. A large 

 (C) and small (D) race of Frontonia is similarly compared — the animals 

 outlined immediately after division.) Unfortunately, it is not clear fi-om 

 Popoff"s statements that he actually saw the unequal divisions which 



Fig. .5. (From Popoff, 1909.) 



are supposed to have originated these new races. And the criticism 

 of Jennings' that Popoff" may merely have isolated pure lines (§ 63) 

 from a mixed population is one which seems both plausible and cogent. 

 74. More convincing are Popoff"s other experiments (1909) on 

 Stentor. This ciliate possesses a meganucleus of a form comparable 

 with a string of beads. By centrifuging an animal which was about 

 to divide, Popoff' caused the nucleus to be unequally distributed to the 

 two daughter-individuals — one receiving 16 "beads," the other only 3, 

 whilst the latter animal was similarly only a quarter of the size of the 



1 See Jennings and Hargitt (1910). 



