242 
R. Ruggles Gates . 
series of geographic sub-species succeed each other down the 
Pacific coast, the most northern form being largest and with 
dark brown markings, while further south they become progressively 
smaller and lighter in colour, i.e., with less brown and more gray. 
These various sub-species are co-terminous with each other in 
their distribution and they form a very close, practically continuous 
series. The conclusion was reached that while such discontinuous 
variations as the red colour phase are independent of environmental 
or functional influence, the continuous type occupying distinct and 
adjacent geographic areas, represents the results of the stress of 
environment on the species in its dispersal, leading to the gradual 
differentiation of local races or sub-species. 
Sumner (1918), in his studies of the deer mice, Peromyscus 
maniculatus , has arrived at similar conclusions regarding the 
occurrence of both mutations and gradual differentiations, and 
their geographic relationships. This subject is one which requires 
much further investigation, but it is at least possible that this 
continuous type of geographic variety in its origin involves the neo- 
Lamarckian factor. 
The neo-Lamarckian principle. 
Experiments have shown that impressed modifications may 
affect the offspring for at least two generations, and to this extent 
the neo-Lamarckian principle has already been justified. The 
mechanism of transmission in such a case is apparently different 
from that of a mutation or a Mendelian character in a cross. The 
latter appears to be determined in the nuclei, and therefore 
transmitted as a stable and permanent feature. The acquired 
character is temporary, cytoplasmic in origin, and will not be 
permanently retained unless re-impressed generation aftergeneration 
until the nuclei of the germ cells are ultimately altered in their 
constitution. 
The fixation of such an organismal character may require a 
longer or shorter number of generations. What determines the 
number of generations required is quite unknown at the present 
time, nor is the modus operandi understood. But we may assume 
that in the process, altered metabolic products in the cytoplasm 
ultimately produce a modification of a chromatin element which 
is permanent in character. It may be expected that such a 
transformation will occur much more rapidly in some cases than 
others. 
