28 Psyche [February 
just as obvious now as when pointed out by Sprengel, but few 
entomologists or botanists will admit its adequate interpretation 
by the simple natural selection idea as believed by Hermann 
Miiller and his followers who did not see the obstacles to this view 
as plainly as did Darwin. 
The attitude of botanists has been affected chiefly by genetic 
investigation. Mendelian research and hypotheses regarding 
mutational evolution have at least gained a serious reconsideration 
of the origin, inheritance, and cause of survival of flower forms. 
Investigations on cross- and self-fertilization, by giving a clear 
and reasonable interpretation of the vigor of first generation 
hybrids and the converse—the apparent deterioration through 
inbreeding hybrids—have caused us to view mechanisms for cross- 
pollination at a new angle. Self-pollination gives inherently 
stranger races (vigor not masked by heterozygosis) and insures 
reproduction, but practically precludes the trial of variations not 
of decisive value or of various recombinations of new variations 
with old characters. On the other hand, cross pollination, while 
permitting the survival of weak types through the vigor of hetero- 
zygosis, and while rendering reproduction more dubious, does 
assure a trial of all new variations in all the combinations possible 
in a mendelian sense. 
The appreciation of the intricacy of the behavior of insects to- 
ward flowers is due primarily to the knowledge of insect sense or- 
gans, to the ingenuity of the experiments of animal psychologists, 
and to the passing of the tendency to interpret all the actions of 
the lower animals as tropisms. 
For these reasons the question as to whether particular flower 
colors have a survival value due to the preference of certain insects 
for them, upon which we have gathered a few data, would probably 
be answered somewhat as follows by the majority of biologists. 
Excluding any question of olfactory sense, it may be assumed that 
insects perceive color differences from short distances but seldom 
if ever exercise a choice. Night flyers, of course, perceive white 
much more easily than colors. These conclusions are supported 
by the data in the following table: 
