522 
David H. Dollev 
phylogeiietically and ontogenetically. For identical types in a species, 
such as the Purkinje cell of tlie cerebellum, upon wliicli the first extensive 
measurements were niade from the dog, it is regarded as no longer a 
theory but a fact. x^ot only do these cells in the saine dog have a constant 
and defmite nucleus-plasma norm, but the saine relation among them 
so far as the data go has been found to hold for different animals of the 
species. This has been confirmed by two of my students for this cell 
in the rabbit. In the Purkinje cell of man, it has been denionstrated 
to apply to the resting ceUs of one case, though it has not been extended 
to other individuals of the species. Unless there has been egregious 
error, in the cells of Canibarus not only corresponding cells of the same 
type in different animals but the majority of ceUs of all types, that is, 
botli niain sensory and motor groups, Start with a uniform nucleus- 
plasma relation represented by a constant coefficient figure. This of 
course is a much broader application than stated above for the dog where 
it was limited to the same type. Even in the crayfish, however, there 
are ceUs undoubtedly of nervous function which have a different nucleus- 
plasma norm and from observation it is apparent that in phylogenetic- 
ally higher ranks of animals there is a greater difference. The relation, 
constant though it would appear to be among corresponding cells of a 
species, evidently differs for different degrees of speciahzation. If the 
constancy of the relation be correct for primitive ceUs, it would seem 
that the change in relation is a most significant fact in differentiation. 
It is to be noted next that this same constant relation not only 
applies to the individuals and averages of the smallest groups but that 
it is maintained subsequently during a considerable increase in their 
size. That is, the increase of size of both these elenients is for a time 
in exactly the same proportion. Consequently, the ciu'ves represeiiting 
this relation remain a straight line (Text Figs. 2 and 4, lower), while the 
figures in Table VII, which is not represented by a curve, vary too littlc 
to constitute an exception, if allowance be made for the smaller number 
of ceUs averaged. In Experiment 23 (Table V, Text Fig. 3), it is to 
be remembered that the smaUest cell is itself advanced in acthdty and 
if corresponding groups be compai'ed in it and Experiment 9, the con- 
stancy of the relation will be seen to hold to the same point of increase 
of volunie. In Experiment 9 (Table IV, Text Fig. 2) and in Experiment 13 
(Table VI, Text Fig. 4), the constant relation is maintained up to double 
the size of the smallest cell. These figures alone niight not be considered 
eonclusive for this point, but the identical findings from the Fmkinje 
cell of three species leave no donbt as to its accuracy. The stage of initial 
