ANIMAL MOTION. 193 



one, and that these hold their feet close to their bodies, 

 during flight, while the long-legged and web-footed birds 

 keep them stretched out.* 



Most of these statements are subject to some exceptions. 

 Among birds which Aristotle probably knew some have only 

 three toes, yet they often fly high, e. g., bustards and golden 

 and some other plovers. Again, the sparrow-hawk, gos- 

 hawk, and harrier, among long-legged birds, and the 

 tern and male pintail-duck, among web-footed birds, have 

 comparatively long tails. Among birds with which 

 Aristotle was probably not acquainted, there are still more 

 striking exceptions, e. g., the secretary-vulture, the Brazilian 

 seriema, the Tropic bird, and Buffon's skua. Further, I have 

 observed that, when in full flight, pigeons, pheasants, black 

 game, and many other birds, which have long or large tails 

 as well as comparatively short legs, carry their feet stretched 

 out backwards, and that some long-legged birds, such as the 

 redshank and storm petrel, often hold their feet downwards. + 



It will be noticed that Aristotle gives to the so-called 

 tail of a bird a special name, orrliopygion, which still 

 survives in the modern anatomical name uropijgium. He 

 was not the first to use the word, for Aristophanes had 

 applied it to the abdominal extremity of a gnat,+ and of a 

 wasp.§ 



On account of his idea that an animal with blood could 

 not have more than four means of progression, he neglected 

 all fins except the pectoral and pelvic, and accordingly he 

 says that the gilt-head and bass have four, the eel and 

 conger two, and the muraena none at all.|| He misunder- 

 stood the nature of the fins of some cartilaginous fishes, e.g., 

 the skate and sting ray, for he considered the large pectoral 

 fins of these fishes to be lateral expansions or " flat parts," 

 for use in swimming.^ 



The cephalopods, he says, swim backwards rapidly by 

 means of their arms and fins, and the crustaceans by means 

 of the hinder parts of their bodies.** He does not seem to 

 take account of the importance of the jets of water expelled 

 through the funnel, in the cephalopods, by means of which 

 these animals propel themselves backwards. He states, 



■■• H. A. ii. c. 8, s. 4. 



f Lists of birds which carry their feet backwards and of some which 

 carry them forwards are given in The Zoologist, 1903, pp. 146-9. 



I The Clouds, 158. § The Wasps, 1075. 



II H. A. i. c. 5, s. 2. «l Ibid. ** Ibid. i. c. 5, s. 3. 







