290 A. FRANKLIN SHULL 



then specifically employed as an argument by either of these au- 

 thors, may have led them unconsciously to the same conclusion. 

 Low temperature caused a relative increase of the nucleus in the 

 Protozoa, low temperature hastened the advent of sexual forms 

 in daphnians; if low temperature also increases the relative nu- 

 clear volume in the daphnids, the Kernplasma theory is again 

 supported. 



In accordance with the above facts, Hertwig and Issakowitsch 

 conceive the ratio K/P to change during the life-cycle as follows. 

 It is least in the early generations descended from the fertilized 

 egg. With continued parthenogenesis and favorable conditions 

 of nutrition and temperature, the ratio increases, the volume of 

 the nucleus increasing relatively more than the volume of the 

 cytosome. Low temperature and deficient nutrition hasten the 

 increase. When a given high value of the ratio K/P is reached, 

 males are produced. With a further shght increase in the ratio, 

 sexual eggs are formed by the fusion of gi'oups of oogonia, and 

 in this fusion the Kernplasmarelation is reduced. 



Issakowitsch ('07) specifically states, and Hertwig's writings 

 imply, that in these changes of the life-cycle it is the Kernplas- 

 marelation of the egg that is concerned. Other tissues, however, 

 were studied by Papanicolau ('10 b) with a view to testing the 

 Kernplasma theory. In conjunction with a number of experi- 

 ments with daphnians, many of the animals from different phases 

 of the life-cycle and from different environmental conditions 

 were fixed. Preparations of the intestinal epithelium, composed 

 of flat polygonal cells, were made. In the paper cited are given 

 figures of these intestinal cells, and in some of them the cells 

 and nuclei are both distinctly larger than in others. While 

 Papanicolau nowhere specifically states that the relative volume 

 of the nucleus is greater in any of these cells than in others, he 

 nevertheless concludes that they support the Kernplasmarelation 

 theory of Hertwig and Issakowitsch. 



The portion of Papanicolau's paper dealing with the Kern- 

 plasmarelation was admittedly a preliminary report. No more 

 extensive investigations have been published, however. I have 

 therefore had photographic enlargements of his figiu'es made, and 



