

' 

 Chap. II.] EXTERNAL CHARACTERS. \Sj, !$'/,> 



_ _____ __ 



hind-limb has been folded forward. Both have then been more 

 or less bent at the joints. But if you fold your own arm back- 

 wards from the typical position into 

 the position indicated for the rabbit 

 (Fig. 5), and then bend it at the 

 joints without further change, you 

 will find that the hand is palm up- 

 wards you must turn the hand 

 over to apply the palm to the sur- 

 F IG . 5.-posmoN OF L.MBS IN f ace? a mo tion that is rendered pos- 

 sible by the partial rotation of the 



outer end of the fore-arm. This further change of position has 

 been effected in the rabbit so as to allow the palmar surface 

 of the maims to rest on the ground. 



4. The Pigeon. The Kock Dove (Columba livia), of which 

 our tame pigeons are domesticated varieties, builds, in cliffs and 

 ruined towers, an untidy nest of sticks and leaves. Here she 

 lays two white eggs, upon which she sits for sixteen days, im- 

 parting to the embryo within them the warmth of her own 

 body. The young, when they emerge from the egg, are pro- 

 vided with patches of yellow down, like (but much scantier 

 than) that which covers the newly-hatched chick. Unlike the 

 chick, which, so soon as it is hatched, is bright-eyed, active, and 

 can feed itself, the little doves are at first quite helpless, with 

 closed eyelids, and must be tended by their parents, who feed 

 them with a creamy fluid secreted by the crop. At the end of 

 three weeks, however, they are fledged, and, after a few days' 

 education by their parents, are able to fly forth and fend for 

 themselves in the world. Those birds which, like the dove, 

 have to be nursed for a while by their parents are called 

 alt-rices ; those which, like the fowl or the duck, are able at once 

 to run or swim and feed themselves, are known as prcecoces. In 

 both development accompanies growth ; but it is more marked 

 in the al trices. 



In the head of the pigeon the facial portion is produced into 

 a horny beak with upper and lower mandibles. At the base of 



