AMICRONUCLEATE RACES OF INFUSORIA 337 



A concrete case will serve to make the point clear. In Para- 

 mecium caudatum, according to Calkins and Cull, the syncaryon 

 divides three times to form eight micronuclei, four of which 

 become transformed into macronuclei and four remain micronu- 

 clei. Since four micronuclei remain micronuclei, the differential 

 which is at the basis of their persistence presumably was insti- 

 stuted or became effective at the third micronuclear division — 

 the division which segregated idiochromatin from trophochro- 

 matin. Calkins and Cull write: 



We have been unable to tell from morphological data which of the 

 first eight somatic nuclei are destined to form four macronuclei; so 

 far as we can tell there is no difference in the chromatin of these nuclei 

 until that swelling begins which characterizes the young macronu- 



cleus Here differentiation takes place, therefore, first by 



nuclear division and second by chromatin metamorphosis, and once 

 transformed. . . . the macronnclcus is ever after a macronucleus 

 until its ultimate dissolution. '- 



Now a cell which received, in the normal course of reconstruc- 

 tion, such a micronucleus and macronucleus would be a typical 

 animal — one in which the idiochromatin and trophochromatin 

 was segregated into distinct bodies. Such an animal would 

 represent the type which experimental work has shown to be, 

 as a rule, non-viable in the absence of a micronucleus. 



On the other hand, it is possible — perhaps probable when we 

 recall the observations of Prandtl and of Patten — that under 

 certain exigencies during cell reorganization the typical course of 

 events may be disturbed so that the differential micronuclear 

 division is suppressed or not precise and all the micronuclei 

 metamorphose into 'macronuclei.' Such 'macronuclei' may be 

 interpreted as amphinuclei. There is, a priori, no reason why 

 nuclei of this character should not be adequate for all the typical 

 life phenomena of the cell, except probably those involving 

 endomixis or conjugation. Such apparently is the potentiality 

 of the nuclear apparatus of the amicronucleate races thus far 

 described. 



>- G. N. Calkins and S. W. Cull, The conjugation of Paramecium caudatum. 

 Archiv f. Protistenk., 1907, Bd. 10, S. 406-407. 



