Psychology. 73 
in the kangaroos and jerboas, in the orders Marsupiaha and Eo- 
dentia. 
There are a good many structures in the skeleton of the Mammalia 
which have not yet received a satisfactory explanation on the ground 
of mechanical necessity. Such, for instance, appears to me to be the 
condition of the history of the origin of the canine tooth; that is its 
use in preference to an incisor for raptorial purposes. Such may be 
also the history of the origin of the complex vertebral articulations 
of the American Edentata, as compared with the simple articulations 
of the Old World. In these, as in similar cases, however, an ele- 
ment enters which must be taken into account in seeking for ex- 
planations; tliat is, that every evolution is determined at its incej)- 
tion by the material or type from which it originates. Thus is 
explained the fact that identical uses have not produced identical 
structures in the limbs of all aquatic animals. The fin of the fish is 
essentially different from the paddle of the Ichthyosaurus or the 
whale, The beak of the rapatorial bird is different from the 
canine tooth of the rapacious mammal. "When this principle is 
duly considered, many mechanical explanations will become clear, 
which now seem to be involved in difficulty or mystery. — E. D. Cope. 
PSYCHOLOGY. 
Grasshopper Keasonin^g. — I was on the railroad train from 
Newport, Vermillion County, for Terre Haute. A grasshopper in a 
heedless spring lit on the glass window of the coach. It was a warm, 
dry, dusty day of the drouthy summer. That little hopper looked 
through the glass and seemed astonished; the car was moving with 
increasing velocity, and thus surrounded by the current of air, the 
quiver and rattle of the car, seemed afraid to jump; and perhaps re- 
calling the terrors of railroad accidents, was too cautious to fall off. 
So, calmly studying the situation, he decided to stay and ride to the 
next station. 
On the polished surface of the giving, dusty glass, his feet became 
dry and his footing insecure. Mental resources came to his rescue. 
His memory and reason notified him that he must keep tlie suction 
cushions of his feet wet to insure an adhesive vacuum. So, after care- 
fully planting his feet in safety, he carefully raised one foot to his 
mouth or lips and moistened it. It was a success, as reason and old 
memories and hopper philosophy had told him. Another and an- 
other foot was so moistened, and the hopper, armed with memorv, 
prudence, and philosophic reason, rode on the train to the next sta- 
