SUMNER — DESERT AND LAVA-DWELLING MICE 
79 
upon the reptiles, as melanistic form.’^^ In each case, considerable 
stress is laid upon the dark coloration of the lava-dwelling forms, it 
being more than once stated that we have to do with ‘‘protective 
coloration.’’ 
It may seem to be worse than reckless for one who has neither seen 
the specimens nor visited the locality under consideration to call in 
question such circumstantial statements by an eminent naturalist. 
It should not be necessary for me to explain, however, that the only 
point at issue is the interpretation of Doctor Merriam’s findings. In 
view of the wholly negative results of my own investigations, to be 
described shortly, I think that I need offer no apology for questioning 
whether some interpretation alternative to that adopted by Doctor 
Merriam is not possible here. 
Two such alternatives suggest themselves. The first of these is that 
the color correspondences observed were due to accident. Mice of the 
same species and subspecies are known to vary widely in color, pale 
and dark specimens being trapped in the same neighborhood. One 
may readily form premature conclusions from an insufficient number of 
specimens, owing to “errors of random sampling.” In the present case, 
it is to be noted that the first of the four named species was represented 
in Doctor Merriam’s collections by two specimens, the second by five 
(two being listed as “somewhat intermediate”), the third by a single 
specimen, and the last by two. Moreover, several of the specimens 
(including the single Perognathus) are listed as “immature,” a cir- 
cumstance which raises the question whether the darker shade of the 
pelage was not due, in part at least, to this fact. 
One would naturally lay less stress upon this first alternative expla- 
nation, particularly since Mr. Vernon Bailey (as he informs me) is 
able to corroborate from his own observation these impressions regard- 
ing the darker pelage of certain rodents of the region in question. 
A second possibihty seems to be more worthy of consideration. It is 
to be noted that in the case of the mammals, at least, the darker race 
was taken in the “pinon and cedar belt,” while the paler race, with 
® It must be insisted that the case of the reptiles is quite different from that 
of the mammals in respect to adaptive coloration. Some lizards, as is well 
known, have chromatophores v/hich are under the direct control of the nervous 
system, and are therefore capable of fairly rapid color adjustments. It may 
well be that many other species possess this power to a less striking degree. On 
the other hand, it would hardly be claimed that mammalian hair is subject to such 
influences. 
