282 H. J. VAN CLEAVE 



A general presentation of the recent results upon the relations 

 between body size and cell size is given by Minot ('98, p. 65) : 



Cells do not differ greatly from one another in size. The range of 

 their dimensions is very limited. This is particularly true of the cells 

 of any given animal. Recent careful investigations have been made 

 upon the relation of the size of cells to the size of the animals, and 

 it has been found that animals are not larger, one than another, because 



their cells are larger, but because they have more of them 



For example, a large frog differs from a small frog or a large dog from 

 a small dog by the number of cells. 



To the writer the foregoing statement has the appearance of 

 too strong a generalization from a limited group of facts. In 

 reality the cells of some animals do differ greatly from one another. 

 Thus in Eorhynchus emydis, while the adult body form is perfectly 

 presented in a small individual 1.7 mm. long, the maximum 

 length of this species is over 30 mm., and both of these individ- 

 uals have identically the same number of somatic cells. Even a 

 most conservative calculation of the relative size of the subcuti- 

 cular cells of the small and the large individuals shows that their 

 ratio based on volume is 1 : 140. Since the subcuticula is a syn- 

 cytium, this calculation is based on the ratio of the volumes of the 

 subcuticula in the two individuals. The volume is determined by 

 taking the product of the length, by the circumference, by the 

 thickness of the subcuticula. Since the number- of nuclei present 

 in the small and the large individuals is the same, the ratio of the 

 volumes of the entire subcuticula of the two individuals is the 

 same as the ratio of the individual cells composing it. It would 

 seem that the range of their dimensions in this case is not very 

 limited. 



Closely associated with this problem of cell size and body size, 

 and growing directly out of it, is the question of the relation be- 

 tween the number of cells present in the organs of the different 

 individuals. In the analysis of any given organ four possibilities 

 of this relation exist: (1) Body size and cell size are both 

 fixed. Of necessity in this instance the number of cells is just 

 as sharply fixed. No case of this sort is known to the writer; 

 (2) Size of the cells is fixed but the body size may vary. Conk- 



