ANATOMY. 297 



good models. A duck swims swiftly and with a mod- 

 erate displacement of water. The propulsive power 

 in the legs and feet is economically displayed. The 

 penguin swims with the combined aid of flippers and 

 feet, and overtakes a fleeing fish. 



While the " lower animals," so called, possess me- 

 chanical principles in their make-up, and the most pro- 

 nounced distinctive qualities, the higher types of life, 

 including man, exhibit in a single individual, the most 

 to admire. One of the strangest creatures amongst 

 the mammalian group is the bat. It wings its way, 

 while catching gnats at twilight, with the ease of a 

 bird, though not with the steadiness of a feathered 

 flyer. The vampire of the tropics is large and fierce, 

 and feeds upon the blood of horses and oxen, unless 

 such stock be corraled and covered with wire netting. 

 In the caves of the West India Islands, there maybe 

 seen by day, suspended from the roofs of grottoes, 

 thousands of bats as large as squabs. 



In early geological times, there were flying 

 dragons of reptilian characteristics ; and smaller speci- 

 mens may be found at present in islands of the Indian 

 Ocean. The wing is a skinny parachute, stretched 

 from one prominent point in the skeleton to another, 

 and is used chiefly as a sail to enable the possessor to 

 glide to quite a distance from higher to lower planes. 

 Flying lemurs have not well developed pectoral 

 wings, like those of bats, but an expanse of integu- 

 ment along the flanks, extending from the fore to the 

 hind limbs. The loose skin is folded or contracted as 

 soon as the aerial animal alights ; then the " wings " 

 disappear, till wanted again in a repeated flight. 

 The extinct pterodactyle of the carboniferous age 

 was not a bat, but a reptilian bird, yet it possessed a 



