164 EDWIN G. CONKLIN 



Berezowski ('11), shows that the cell size is slightly greater in 

 castrated mice than in normal ones. 



In a series of briUiant studies, Jennings ('08, '09, '10, '11, etc.) 

 has shown that at least eight different races, or 'pure lines,' of 

 Paramecium may be distinguished by their size. The mean 

 length of the largest race is to that of the smallest about as 5 : 1. 

 While the variations in length within each race is considerable, 

 the norm for each race is quite characteristic. He finds that the 

 differences in size between individuals of the same race are due 

 to growth and environment and are not inherited, whereas the 

 differences between different races are inherited. 



In addition to the foregoing references there are doubtless many 

 other observations on the relations of cell size to body size scat- 

 tered through the literature. These references, however, are 

 believed to include the most important works on this subject, 

 as well as the principal conclusions which have been reached. 



The following observations on the relative size and number of 

 cells from the bodies of different species of Crepidula, and from 

 different individuals of the same species were made many years 

 ago, and a brief note on this subject was published at that time 

 (Conklin '96), and a somewhat more complete account in a sub- 

 sequent paper ('98). 



1. CELL SIZE AND BODY SIZE IN DIFFERENT SPECIES OF 



CREPIDULA 



I have made no extensive study of cell size in relation to body 

 size in different classes of animals, most of my work having been 

 confined to different species of gasteropods, and principally to 

 the genus Crepidula. Without any special study on this subject, 

 however, it is quite evident from casual observation that different 

 classes differ widely in cell size, and that these differences are not 

 usually correlated with differences in body size. The great size 

 of cells in amphibians, nematodes and some insects is well known, 

 whereas in echinodcrms, annelids and mammals the cells are 

 relatively much smaller. Even different species, and varieties 

 of the same species, may show considerable differences in cell 

 size, as Strasburger, Gates and Boveri have shown. 



