1878.| Relation of Animal Motion to Animal Evolution. 45 
articulations display an interlocking or tongue and groove char- 
acter. The same thing is seen in the ulno-radial fixed articula- 
tion in the same types. These arrangements are especially ad- 
apted to prevent dislocation by side strains, andif the preceding 
explanations be true, this structure is a corrugation due to the 
lateral pressure of a more or less convex surface, on a concave 
one which embraces it, and vice versa. : 
In the circulatory system pressure has doubtless played an im- 
portant part. Increased oxygenation of blood, the necessary con- 
sequence of the purification of the atmosphere, would stimulate 
the action of all the organs, including that of the heart. Greater 
pressure on its walls and septa would increase their size and 
strength, and ultimately close such foramina, as were not in the 
course of the blood current; as the foramen septi ventriculorum of 
_ reptiles and the f ovale. Increased force ofthe current would, on 
= the other hand, soon cause the enlargement of one or other of the 
four or five pairs of primary aorta bows, and develop it at the 
expense of the others, until finally the pre-eminence of one chan- 
nel be secured and the aorta be the result. This part of the sub- 
ject might be prolonged to an unlimited extent, but the above 
illustrations must suffice to indicate the meaning of my propo- 
sitions. 
Se se Ge RR ale ee ESEN TWLA Rn A Meee MEERN SAS ee ere ep ag ee ee eee A 
1 Pee E gee ae 
it Sa A ka ah 
III. 
That movements change the environment of a plant or an ani- 
mal, or parts of them, is obvious enough. If we consider only 
the reflex class, to which all the movements of plants and many 
of those of animals belong, we perceive that but for them the or- 
dinary functions of assimilation, circulation, -etc., could not be 
performed; there would be no change inthe contents of their 
tubes and cells, and the environment of these would be unaltered. 
But when we view the movements of the higher animals, we per- 
_ ceive the immense importance of the powers and organs of move- 
ment as a factor in evolution. It may be safely assumed, that 
without powers of designed or adaptive movement, life would 
never have advanced beyond the stage presented by the vegetable 
kingdom. 
The stimuli which are effective in animal consciousness are four, 
viz: excessive temperature, hunger, danger from enemies, and 
_ the reproductive instinct. These prompt to the movements which 
_ we observe in animals in a wild state, and without which it is evi- 
_ dent that the animals themselves would soon cease to exist. 
