How to Solve One of the Problems of Science [pp. 787-793]

How TO SOLVE ON~E OF
lace holds that color changes have their root in protective
value), yet it is certainly a step in advance to have ascertained the chemical phenomena which go along with these
outward changes. It is interesting, too, to find a relation between color and constitutional strength. De Varigny tells us
that certain poisonous plants produce no effect on dark-colored
animals; while to light-colored animals the same plants are
deadly. Climate also affects the size of animals and plants.
But a change in dimensions is accompanied by other changes.
When dimensions vary, sexual fertility not seldom varies with
them. External influences have also much to do in determining sex. When tadpoles, for instance, are left to themselves
the females slightly outnumber the males; but when they are
fed on beef, the proportion rises from 54 to 78 per cent.; and
when given frog-flesh to eat, the proportion of females increases
to 92 per cent. Bees, too, are similarly influenced: among
them the birth of queens, workers, and drones is largely a
question of food. Now, the external factors which determine
sex in these and in many other cases require careful study.
It may be asked, why fish are small in small streams? Here
the experiments of De Varigny rather go to show that diminished size is owing to diminished space to move about in: impediments to movement would seem to have a tendency to
dwarf the organism.
May not this also be the reason why animals living on
islands are smaller as a rule than the same species living -on
continents? The elephants whose fossil remains have been discovered in Malta were exceedingly small. But here again
more exact experiments are needed. It is also interesting to
find that in regions where thorny, spiny plants abound the
snakes in such places evince a similar tendency, as Professor
Cope tells us of the horned rattlesnake of New Mexico and
Arizona. What is the mysterious bond existing here between
the plants and the rattlesnakes? It is also interesting to observe
how subject the perfume of flowers is to variation. In rich
soil the increased strength of the plant is accompanied by increased perfume; while in poor, sandy soil a contrary effect is
produced. The hairy covering of a plant grown on a mountain
disappears when it is transplanted to a valley; but the hairs
reappear when it is brought back to its mountain home.
Wallace tells us that the skeletons of animals vary, especially the skeletons of whales; and St. George Mivart finds that
the number of ribs in the ape and in man is subject to varia