394 



NOTES. 



163 rp^ e g urmam Toad has no tongue. 



164 The posterior pair of limbs is sometimes represented by a pair of small 

 bones ; and the Boas and Pythons show traces of external hind-limbs. 



165 There are some notable exceptions. The Slow- worm is legless, and 

 the Chameleon has a soft skin, with minute scales. 



166 According to Owen ; but Huxley insists that the plastron belongs to 

 the exoskeleton. 



167 Knees always bend forward, and heels always bend backward. 



168 We cannot claim that this airy skeleton is necessary for flight. The 

 bones of the Bat are free from air, yet it is able to keep longer on the wing 

 than the Sparrow. The common Fowl has a hollow humerus ; while some 

 Birds of long flight, as the Snipe and Curlew, have airless bones. 



169 The fossil Archceopteryx, a lizard-like Bird, is placed in a separate di- 

 vision, Saururce. Birds have also been divided according to their degree of 

 development at birth into (I) Hesthogenous, as Fowls, Ostriches, Plovers, 

 Snipes, Rails, Divers, and Ducks, whose chick is hatched completely clothed, 

 has perfect senses, runs about, and feeds itself. When full grown, it uses its 

 feet rather than wings, flying with a rapid, labored stroke, and taking the 

 first opportunity to settle on land or water, not on trees ; the male is po- 

 lygamous and pugnacious ; the female makes little or no nest ; and neither 

 sex sings. This group is of the best use to man, and approaches more near- 

 ly to Mammals, the habitual use of the legs and preference for land or water 

 degrading it as a Bird and raising it in the list of animals ; (2) Gymnogenous, 

 as Gulls, Pelicans, Birds of Prey, Herons, Sparrows, Woodpeckers, and 

 Pigeons, whose chick comes helpless, blind, and naked ; it can neither walk 

 nor feed itself, but gapes for food ; the adult is monogamous, and builds 

 elaborate nests in trees and perches ; many sing ; all are habitual fliers. 

 These are birds par excellence, gifted with higher intelligence than the 

 others, and are never domesticated for food. 



170 Hopping is characteristic of and confined to the Perchers ; but many 

 of them, as the Meadow-lark, Blackbird, and Crow, walk. 



171 This order is artificial. But it is better to retain it until ornithologists 

 agree upon some natural arrangement. The classification of birds is taken 

 from Coues's "Key to North American Birds," as being the work on orni- 

 thology in most general use. 



172 The Whales are hairy during foetal life only. 



173 The Manati has 6 ; Hoffmann's Sloth 6 ; and two species of three-toed 

 Sloth have respectively 8 and 9. 



174 As in the Whale, Porpoise, Seal, and Mole. Teeth are wanting in the 

 Whalebone Whales, Ant-eaters, Manis, and Echidna. 



175 The Monotremes resemble Marsupials in having marsupial bones, but 

 have no pouch. They differ from all other Mammals in having no distinct 

 nipples. 



176 The pouch is wanting in some Opossums and the Dasyurus. 



177 For the best account of the Elephant, see Tennant's "Ceylon" or 

 Brehm's " Thierleben." 



178 The fore-feet of the Tapir have four toes, but one does not touch the 

 ground. 



