912 The American Naturalist. [October, 
no longer, and to become automatic, and a part of the men- 
tal furniture. That the use of words has been the cause of 
an acceleration of rational development in man there can be no 
doubt; but the mentality of the lower animals contradicts the 
supposition that it was entirely essential. 
Many of the mammalia understand human language. They 
understand the meaning of words apart from tone and gesture. 
This can be most frequently seen in dogs, some of whom become 
remarkably expert in carrying out orders from their masters. 
Examples of this kind are familiar to many persons. Now the 
giving of orders involves the use of verbs. Verbs do not repre- 
sent objects, nor do they represent even single acts, but they 
express a class of single acts. In the comprehension of a verb, 
a dog performs an act of simple generalization, distinctly above 
the mere recognition of an object by a name. 
Induction —Most evident is the existence in animals of the 
faculty of induction, which involves a generalization; z.e., the 
drawing of a single general inference from a number of 
instances. While pure conception expresses cognition only, in- 
duction infers action on the part of its objects. From such and 
such premises, such and such events will follow, either as coin- 
cidence or as effect. 
I now give some illustrations of experiential inference, and 
deductive or practical application, among the lower animals. 
A great many animals adopt methods of concealment to es- 
cape observation, both of enemies and of the prey they seek. 
Certain species of crabs attach to their carapace pieces of alge, 
which then vegetate and cover the animal with a growth which 
conceals it. Others carry a stone above the posterior part of the 
carapace, which serves as a basis of attachment for foreign or- 
ganic growths which conceal them. Still others permit the 
growth of sponges and actiniz on various portions of their sur- 
face, which sometimes cover them completely from view. Among 
birds peculiar attitudes are adopted, which serve as an effective 
concealment ; such are those of some of the herons, which stand 
bolt upright in growths of reeds and thickets, so as not to be 
distinguished from the surrounding stems and trunks. So the 
