10 The American Naturalist. [January,. 
Turning again and for the last time to the doctrine of inter- 
mediate end-processes, we come as I suspect, under its combina- 
tion with the postulate of many primitive senses to the particu-- 
lar combination of possibilities most likely to accord with the- 
truth, and which therefore, must solicit the attention of future 
investigators. Yet for olr present purposes of merely schedul-- 
ing the different possible categories, and the general plan of 
each, it is perhaps sufficient, after what we have said of the 
other case, to state of the present ones as follows. 
(Miw). Under the Weismannian principle, with many 
primitive senses, and complex end-processes, the resulting pro- 
gramme and the reasons therefor should easily be constructed 
by modifying our third and seventh last above paragraphs. 
(Oiw and Mdv). 
(Mil). And under the Lamarckian principle the correspond- 
ing programme should be easily constructed by modifying 
paragraphs third, seventh and tenth now last above. (O41, 
Oil, and M4@}). 
Finally we must observe regarding all the above possibilities 
that it is not necessary that any one of them should have pre- 
vailed universally. In other words it is logically possible that. 
some one of them should have ruled in the production of one 
of our senses, and another sense have followed quite a different 
course. Thus while it is quite possible that light is the direct. 
stimulus of color sensation, as Prof. Wundt thinks, and always 
has been, yet it may be that the final stimuli for our heat and 
cold sensations are certain processes of mechanical contractions 
and expansions among different tissues, which processes are 
intermediate between the nerve impulses and the physical 
modes of motion called heat and cold; or, directly the reverse 
of this may have been true. Moreover it is possible that cer- 
tain of our above categories may have prevailed at one period, 
and another at another; though this could not apply to all 
the categories, some of them being mutually exclusive. 
Such is the field of our problem. It is doubtful if there is an- 
other that has been equally neglected, or that presents greater 
confusion. Yet because of its importance there is still required 
of us to consider what avenues offer themselves for solving its 
