90 University of California Publications in Zoology. [Vol.6 



ir.il times the region has certainly undergone, but how much 

 and what effect on the water and bottom conditions this might 

 have had, we can surmise only in the vaguest way. Or, assuming 

 migration instead of local change to account for the altered en- 

 vironment, where was this original home and in exactly what 

 way did it differ from the newly-reached home? At best, an- 

 swers to these questions must fall far short of proof. 



Again, what were the characters of the ancestral species which 

 through linkage with the assumed changing environment were 

 transformed into the characters of //. johnsonil Really, is it 

 no1 well-nigh certain that we are forever shut away from any- 

 thing even approaching proof as to how this particular species 

 with which we are now occupied came to be what it is? Is there, 

 then, any line of inquiry concerning the clear though complex 

 fact of adaptation in //. johnsoni that promises a more satisfac- 

 tory issue than the inquiry as to how the adaptations arose? 



Some paragraphs back we agreed to accept "provisionally" 

 the view that "change of environment and of environed organism 

 are wholly and inseparably linked together." Suppose we fix 

 attention on this proposition for a little. If we do this, are 

 we not at once compelled to say that "only in a general way" 

 are we prepared to maintain the truth of the proposition? One 

 of the cardinal positions in these inquiries is that we are not 

 to rest satisfied with what is true in a general way only. We 

 are. in spirit at least, committed to the resolution of these gen- 

 eral truths into their more special parts. Is there not. then, some 

 way of getting a firmer hold upon the problem of how closely 

 the species is linked to its environment other than by attempting 

 to follow it and its environment into a past that is forever be- 

 yond the reach of observation, or into a future so remote that 

 only generations yet unborn may lay hold upon it.' 



The space-range of the species affords an approach to the 

 problem that has at least the advantage of being far more 

 accessible to present observation than does the time-range. It 

 is, therefore, surely desirable to travel this way as far as pos- 

 sible. Let us, then, take to it in earnest. First, let us look at 

 the conditions under which the species lives within its own range. 

 The questions that would seem to reach the supposition of close 



