152 BAILEY AND TUPPER. 



Berezowski (1910), Yapp (1912), Schramm (1912) and Paulmann 

 (1915) are particularly significant, since they show very clearly that 

 the size of the cells of a given tissue may vary considerably in differ- 

 ent parts of an organ or individual and during different stages in its 

 growth or ontogeny. 



Hertwig (1903) notes the importance of the fact that the "Kern- 

 plasmarelation" is subject to considerable variation during the life of 

 a cell and, therefore, determines this ratio during a particular phase in 

 the development of cells. The results of Conklin's (1912) work upon 

 Crepidula plana are of interest in this connection. He states (p. 25) : 

 "The results of my measurements do not indicate that the Kern- 

 plasma-Relation of Hertwig is either a constant or self regulating 

 ratio in the blastomeres of these eggs; on the other hand it appears 

 to be a result rather than a cause of the rate of cell division, and 

 consequently it is a variable rather than a constant factor. Further- 

 more, the size of the nucleus, in these eggs, is dependent upon at least 

 three factors: (1) The initial quantity of chromatin (number of 

 chromosomes) which enter into the formation of the nucleus (Boveri). 

 (2) The volume of the protoplasm in which the nucleus lies. (3) The 

 length of the resting period." 



The necessity of distinguishing between purely somatic variations 

 in cell size and those that are truly germinal, is fully appreciated by 

 Jennings (1908), in his careful work upon unicellular organisms. On 

 the botanical side, Zalenski (1904), Kolkunow (1905, 1907, 1907a and 

 1913) and Jakushkine and Wawilow (1912), in a series of important 

 papers published unfortunately in Russian, show that, although the 

 size of the stomata and guard cells vary considerably in different parts 

 of an individual and under different environmental conditions, there 

 is an inherited norm which varies in different races or varieties of our 

 commonly cultivated cereals. They find that certain of the larger 

 races possess larger stomata, but this is not true in all cases. In his 

 study of nanism, Sierp (1914) emphasizes the necessity of differen- 

 tiating between true constitutional dwarfs and depauperate plants. 

 He comes to the conclusion that the latter have smaller cells than 

 normal, but finds three classes of inherited dwarfing; dwarfs of Pisum, 

 Solanum, Zea and Clarkia have smaller colls than normal, those of 

 Nigella larger cells than normal and those of ]\Iirabilis and Lathyris 

 cells of normal size. Unfortunately he does not record the size and 

 number of chromosomes in the material investigated by him. 



It is evident, accordingly, that not only may different types of size 

 variations occur in different categories of tissues, but also in different 



