Chap. I. RUDIMENTS. 23 



whole external ear being permanently pressed back- 

 wards. In many monkeys, which do not stand high in 

 the order, as baboons and some species of macacus, 23 the 

 upper portion of t^e ear is slightly pointed, and the 

 margin is not at all folded inwards; but if the margin 

 were to be thus folded, a slight point would necessarily 

 project inwards and probably a little outwards. This 

 could actually be observed in a specimen of the Ateles 

 beelzebuth in the Zoological Gardens ; and we may safely 

 conclude that it is a similar structure — a vestige of 

 formerly pointed ears — which occasionally reappears in 

 man. 



The nictitating membrane, or third eyelid, with its 

 accessory muscles and other structures, is especially 

 well developed in birds, and is of much functional im- 

 portance to them, as it can be rapidly drawn across the 

 whole eye-ball. It is found in some reptiles and amphi- 

 bians, and in certain fishes, as in sharks. It is fairly 

 well developed in the two lower divisions of the mam- 

 malian series, namely, in the monotremata and marsu- 

 pials, and in some few of the higher mammals, as in the 

 walrus. But in man, the quadrumana, and most other 

 mammals, it exists, as is admitted by all anatomists, as 

 a mere rudiment, called the semilunar fold. 26 



The sense of smell is of the highest importance to 

 the greater number of mammals — to some, as the rumi- 

 nants, in warning them of danger ; to others, as the 



85 See also some remarks, and the drawings of the ears of the Lemu- 

 roidea, in Messrs. Murie and Mivart's excellent paper in ' Transact. 

 Zoolog. Soc.' vol. vii. 1869, pp. 6 and 90. 



26 Muller's ' Elements of Physiology/ Eng. translat., 1842, vol. ii. p. 

 1117. Owen, 'Anatomy of Vertebrates,' vol. iii. p. 2G0 ; ibid, on the 

 Walrus, ' Proc. Zoolog. Soc.' November 8th, 1854. See also E. Knox, 

 • Great Artists and Anatomists,' p. 10G. This rudiment apparently is 

 somewhat larger in Negroes and Australians than in Europeans, see Carl 

 Vogt, 4 Lectures on Man,' Eng. translat. p. 129. 



