finely he has elaborated the contrast between the esthetic characters of the two senses.
What, it will be asked, of the lower animals that have no external ear, or have one that can not be moved? In regard to such, we must carefully distinguish those species which have never possessed the movable ear from those which have lost the power of movement. It is the loss of a faculty once possessed that we are at present more immediately concerned with. Yet, in the case of such animals as the birds, which, though endowed with a highly developed sense of hearing, have no external ear, it is interesting to observe that there is remarkable appreciation of music. And this is not merely a response to individual sounds, as the musical appreciation of some animals may be; there seems to be an enjoyment of melody. Browning happily described the thrush as 'wise' because the bird 'sings each song twice over,' and thus shows his ability to 'recapture'
It is also to be noticed that many birds can imitate other sounds, even those of the human voice. The repetition may be 'parrot-like,' but it gives evidence of the power of attending to a series of sounds.
It should be mentioned that the external ear of certain aquatic mammals is atrophied or lost. But as these animals have taken to a different kind of environment, and have been to so remarkable an extent made over, it seems unnecessary in the present investigation to give special consideration to this particular change in their structure.
The case of the monkeys seems at first to be different. Some of them, the anthropoid apes at least, have like man lost the power to move the ears, yet they have not, it may be said, the faculty of speech. Have we not, then, the loss without any compensation of the special kind that is here being claimed for man? In considering this question we must keep in view the psychologist's ignorance of the mental life of the monkey. Notwithstanding all that has been written of the relationship of man to the monkeys, the psychology of these animals is still for the most part a blank. Yet there are some significant data that may in the present case be appealed to. The howling monkeys, though of low intelligence, find delight in the noise, from which they receive their name. They are gregarious and they howl in company. This noise is not made to drive away enemies; the monkeys gather deliberately for the purpose of making the noise and the leader starts the concert.
The chattering of monkeys should also be regarded as affording
- "The more recent ape ancestors, common to men and to the anthropoid apes (gorilla, chimpanzee, etc.) discontinued the habit of moving their ears and hence the motor muscles gradually became rudimentary and useless." Haeckel, 'Evolution of Man' (English Translation), Vol. II., pp. 270-271.