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THE AMERICAN NATURALIST 



[Vol. XLIX 



cells and protozoa, may not also take place in the case of 

 the somatic, especially of tumor cells. Without consider- 

 ing any connection with the problem of the immortality of 

 the somatic cells, Bashford, Murray and Bowen 12 stated 

 on an empirical basis that in charting the number of suc- 

 cessful inoculations of a mouse carcinoma in mice, in 

 different generations and in different strains of the same 

 generation, they noticed definite rhythmic variations in 

 the number of successful inoculations, a maximum of suc- 

 cessful inoculations in one generation being followed by 

 a minimum in the succeeding generation. However, they 

 also state that parallel strains of the same tumor did not 

 show maxima or minima at the same time. Bashford, 

 Murray and Bowen, in order to explain these observations, 

 assumed that different parts of the same tumor show 

 different degrees of growth energy at the same time; this 

 would imply that such areas differing in growth energy 

 at the same period are separated through transplanta- 

 tion ; so that in one generation mainly energetically grow- 

 ing pieces are used for transplantation in the succeeding 

 weakly growing pieces almost altogether, an assumption 

 which does not appear very probable. 



Calkins 13 held that there occur in succeeding genera- 

 tions not so much rhythmic variations in the number of 

 successful transplantations as in the growtli energy of 

 the tumors. He compared these rhythmic variations with 

 the rhythms observed by him in the case of P aroma cium. 

 However, such rhythms were not noticeable in the mouse 

 carcinoma which we have propagated for a number of 

 years in our laboratory, as has been shown by Mover S. 

 Fleisher. 14 He furthermore shows that even in the case 



