Page:Popular Science Monthly Volume 28.djvu/342

 arc concerned, than many other vertebrates. In fact, in Romanes's work on "Animal Intelligence," the highest powers of intellect are ascribed to the carnivora, which as a general rule are solitary animals. And this is a natural result of the fact that they are obliged to depend upon their own powers in all the exigencies of life, and can not trust to others to relieve them from some of the duties of existence.

Much has been said about the highly remarkable powers of the minute mass of nerve-substance in an ant's head. Yet the brain of every animal has undoubtedly a double duty to perform. It is partly devoted to the control of the muscular organization, partly to psychical activity. And to this we must ascribe the increase in size of brain that generally attends increase in size of body among animals. Though the brain of a large animal may be much larger than that of a small one, this may be mainly due to the increase of its motor duties, and there may be no increase in its psychical portion. In fact, in certain large extinct animals, with greatly developed posterior structure, a sort of second brain seems to have existed at the rear extremity of the spinal column, as if the motor portion of the brain had moved backward to the region where it was most needed. Yet it is very probable that in any of the higher vertebrates the portion of the brain devoted to psychical functions is considerably greater in volume than the whole brain of the ant. And, if the degree of intelligence be in any sense proportional to the size of its organ, these higher vertebrates should be superior in intellect to the ant.

Such is actually the case. The excursions of the ant-mind beyond the limit of its instincts seem to be exceedingly slight. Those of the mammalian mind are sometimes extensive. If we compare the instances of individual intellect displayed by a cat and an ant, for instance, we can not avoid the conclusion that the cat is very greatly superior in powers of reasoning. Yet no cat tribes keep cows, marshal armies, store provisions, enslave captives, or perform any of the wonderful series of intellectual acts which are common in ant communities, and which form part of the powers of every ant-brain. How shall we account for this difference in results? It seems evident that it is in some way due to difference in modes of association. The powers of the ant are instinctive—that is, they have been passed down by hereditary transmission through numerous generations. They are the outcome of not one brain, but of innumerable brains. Though the brain of one ant be minute, yet the brains of a million ants would form a considerable mass, and every act of ant intellect is probably the product of several millions of ant-brains, each of which may have added some minute increment to the final result.

There are, in fact, two distinct methods by which the intellectual powers of ancestors may be transmitted to descendants. One of these is the hereditary, the other the experimental. Among solitary animals the special intellectual achievements of each animal are in great