320 DAVID H. DOLLEY 
been made in previous work (’14, p. 494), and more strongly sup- 
ported in some unpublished work, that function is the sole deter- 
minant of absolute size. Non-divisional growth in mass is a fune- 
tional growth. Here are two animals born together and living 
under functional conditions as identical as may be. Their cells 
show the same absolute size. It is a noteworthy verification of 
the deduction. 
It fits in with this relation of function to size that the evi- 
dence is accumulating of a tendency to a ‘uniformity of absolute 
size among corresponding nerve cells of animals of the same spe- 
cies. When sufficiently demonstrated it would be understandable 
on the basis of average general functional usage. The excep- 
tions thereto so far in the dog, the unusually large cell, have 
been associated with a known history of unusual training and 
activity. It makes the nerve cell agree with Conklin’s conclu- 
sion that within the same species cell size is approximately con- 
stant. Making simply a statement here of the probable prin- 
ciple, it is to be noted that these two dogs, being not yet grown, 
offer no evidence for or against species uniformity of absolute 
size, save that they are progressing together under identical 
conditions. 
It might be expected and to some extent it is true that all 
stages succeeding stage 1, being based quantitatively upon it, 
might show this same correspondence of absolute size. How- 
ever, in all stages except stage 1, one encounters a shifting range 
of size throughout the stage. The results will vary according as 
the majority of cells are at one end or the other, or well distrib- 
uted in the chance of a section. Stage 1, though there are inter- 
mediate grades to stage 2, was frankly selected in both animals 
as the nearly flat type, with this very point in view, and inter- 
mediate stages were thrown to stage 2. 
THE INCONSTANCY OF COLLECTIVE AVERAGES OF FUNCTIONING 
CELLS 
It only remains to demonstrate from the data in table 3 the 
inconstancies which may result from averaging all cells irrespec- 
tive of their functional state, and to expose the fallacy of deny- 
