18 LORANDE LOSS WOODRUFF 



(ten-day period 24, part A). This vacuolization of cytoplasm 

 and nucleus is not peauliar to the race of Oxytricha under obser- 

 vation, as similar phenomena are mentioned by other students 

 of the life history of Infusoria. 



Conklin ('12) first called attention to one aspect of this 

 question : 



Neither Minot nor Hertwig took account of the fact that a large part 

 of the nuclear content belongs to both nucleus and protoplasm. The 

 Kernplasmarelation depends very largely upon the quantity of proto- 

 plasmic material temporarily in the nucleus Neither t)f 



the authors named, in describing the enormous growth of the nuclear 

 material during cleavage, took account of the growth of the protoplasm 

 during cleavage at the expense of the yolk. 



This, it seems to me, emphasizes a fundamental difficulty in 

 many studies on the nucleo-cytoplasmic relation, and one which, 

 in somewhat different aspect, has to be considered in the present 

 work. The vacuolization of cytoplasm and nucleus in all prob- 

 ability does not represent strictly a reversible interchange of 

 material between these two elements of the cell, but it certainly 

 indicates a dilution of the fundamental constituents of .the cyto- 

 plasm and nucleus (employing these terms in their usual sense) 

 and, insofar as this is true may, and undoubtedly does, alter the 

 proportion. 



The question of importance, then, is whether the increase in 

 size of cytoplasm and nucleus, and the decrease in the relative 

 amount of nuclear to cytoplasmic material, which has been 

 shown to occur in this race with declining reproductive activity 

 (periods C and D), indicates an actual change in these elements or 

 whether the vacuolization is sufficient substantially to alter the 

 results. A careful study of the cells with this in mind shows 

 unmistakably that the cytoplasm and the nucleus, in the strict- 

 est interpretations of these terms, actually increase in volume 

 with decreased fission rate. The mean difference in nuclear size 

 and cell size between periods A and B, and B and C are of such 

 a magnitude as to be clearly beyond any error due to vacuoliza- 

 tion. Careful study also shows that the vacuolization which is 

 present in part C is not sufficiently extensive appreciably to 

 affect the nucleo-cytoplasmic relation. 



