1882. 165 Trans. N. Y. Ac. Sct. 
change of shape of the entire mass of the unicellular body. The power 
of movement here resides in the unorganized protoplasm, without any 
organs whatever. Even in the lowest form of life there is a conver- 
sion of Vztal force into Physzcal force. 
Higher in the animal scale we find motion by means of cilia. These 
are minute elastic laments which have a whip-like motion—alternate 
flexion and extension. But the cilia do not seem to be controlled ne- 
cessarily by the creature’s will. The motion is evidently automatic. 
Many low plants, as well as animals, have the body covered with cilia 
by which they tumble about in the water very lively. In some of the 
infusorians, however, the cilia seem to obey the animal’s will. 
The means of motion in all higher animals is muscular tissue. This 
is a highly specialized tissue, subjected to the nervous system, and 
which concentrates the power of movement, which in the amoeba 
was diffused through the whole mass of the body. Muscular power 
resides in the contractility of the cells. Expansion of the cells or the 
extension of the whole muscle is produced by elastic reaction—a 
merely physical force —or by contraction of opposing muscles, Mus- 
cles act under nervous, electric or other stimulus; but sometimes no 
stimulus seems necessary. 
The organs and methods by which the vital contractile force of 
muscular tissue is utilized in producing mechanical power is a most 
interesting study. [With the magic lantern a few of the more typical 
and interesting methods of locomotion in animals were shown.] 
A few animals move without organs, as the sea-anemone in crawl- 
ing or the jelly-fish, leech, and snake in swimming. But most ani- 
mals have parts or organs specially adapted to locomotive purposes, 
The old classification of swimming, flying and walking will answer our 
purpose. 
Loconotion in water requires much less effort than locomotion in 
the air, and more than locomotion on solids. But the organs tor swim- 
ming are comparatively simple. The lobster swims backward by its 
tail fin, which is a combination of beautiful oars. The squid swims in any 
direction, by ejecting the water of respiration out of a flexible tube. 
Swimmers far excellence are the fishes. They propel themselves 
chiefly by their tail fin, used as a horizontal scull oar. The remaining 
fins are used to guide and control the motion. The paired fins are 
based upon the arm and leg bones. The rays fly through the water by 
means of the pectoral fins and side expansions of the body. The 
whale propels himself by the vertical motion of the body and tail 
Frogs, turtles, crocodiles and many birds are especially adapted to a life 
in water. 
Locomotion in Atry.—On account of the extreme rarity of the atmo- 
