C. DOBELL 159 



former. Both individuals reorganized themselves successfully after 

 fission, and continued to multiply normally for about a week'. They 

 produced giant and dwarf races respectively, according to expectation. 

 It was also ascertained that the individuals of the smaller race had 

 reorganized their meganuclei so that they consisted of the normal 

 number of " beads." 



75. In another experiment Popoff (1909) suddenly cooled a Stentor 

 which had begun to divide. The division was thus made to regress. 

 Placed at a norma! temperature, the animal then reorganized itself in 

 a peculiar way into a single individual. It then gi-ew to a very large 

 size, and subsequently divided. A race of giant Stentors was obtained 

 in this way which continued to divide and breed true for as long as the 

 culture was kept (about li months). [The size of this race can be 

 gauged from Fig. 5, E, which shows a dividing individual drawn to the 

 same scale as the other Stentors, A and B.] The karyoplasmic ratio of 

 the giant individuals ajjpeared to be the same as that of the normal 

 race from which they were derived. One of the giant Stentors from 

 the race just described is said to have divided unequally into a large 

 and a small individual. From the former, an even larger race was bred. 

 All attempts to obtain still larger races failed. 



76. Popoff (1909) tried to produce new races of Stentor by cutting 

 off pieces of protoplasm from an individual and so changing the karyo- 

 plasmic ratio. The experiments were inconclusive, though it is stated 

 that a small piece of a Stentor containing a small piece of nucleus can 

 reorganize itself into a small individual capable of dividing several 

 times — always forming small individuals. Death always followed, how- 

 ever, and no small race was produced in this fashion'-. It is to be 

 hoped that all Popoff's experiments will soon be repeated by other 

 workers. 



77. Somewhat similar experiments have been made on Paramecium 

 by Calkins (1911) and Peebles (1912), and the latter concludes: "The 

 removal of a portion of the cytoplasm does not result in the production 

 of smaller individuals. After several generations have been produced 

 the normal size is regained." 



1 The cultures were then lost. 



- Kegeneration has, of course, been studied in some detail in Stentor — e.g. by Balbiani 

 (1888, 1892, 1893), Gruber, etc. But I know of no record of the production of a race of 

 different size as a result of mutilation. It seems probable, moreover, that vivisected 

 Stentors sooner or later reorganize their meganuclei so that they consist of the normal 

 number of "beads.'' (Cf. Balbiani (1888, 1893), Prowazek (1904), etc.) 



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