382 NOTES. 
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 opportu- 
nity to settle on land or water, not on trees; the male is polygamous 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 nearly to Mam- 
mals, the habitual use of the legs and preference for land or water degrad- 
ing it as a Bird and raising it in the list of animals; (2) Gymmnogenous, as 
Gulls, Pelicans, Birds of Prey, Herons, Sparrows, Woodpeckers, and Pig- 
eons, whose chick comes helpless, blind, and naked; it can neither walk nor 
feed itself, but gapes for food; the adult is monogamous, and builds elabo- 
rate 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. 
91 We can not 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. 
192 Hopping is characteristic of and confined to the Perchers; but many 
of them, as the Meadow-lark, Blackbird, and Crow, walk. 
193 This order, founded on the disposition of the toes, is purely artificial. 
But it is better to retain it until ornithologists agree upon some natural ar- 
rangement. 
194 In the Swifts and Goatsuckers, the hind toe is versatile, being turned 
sideways, or even forward; while the third and fourth toes of the Kingfish- 
er are united, and its wings are short. 
195 The Whales are hairy during foetal life only. 
196 The brain of Mammals differs also from that of lower Vertebrates in 
that the lobes of the cerebrum are connected by a band ealled corpus callo- 
swum, and the lobes of the cerebellum by the pons Varolii. 
197 As in the Whale, Porpoise, Seal, and Mole. Teeth are wanting in the 
Whalebone Whales, Ant-eaters, Manis, and Echidna. 
128 An acceptable classification of Mammals is still a desideratum. Owen’s 
subclasses, founded on the structure of the brain, and De Blainville’s (adopt- 
ed by Huxley and Gill), founded on the nature of the reproductive organs, 
are unsuitable for a text-book. It is sufficient to state here that the two 
lowest orders are implacental, and their young are born in a very imperfect 
condition; while all the rest are placental, whose embryos are more com- 
pletely formed before birth, being connected with the blood of the mother 
by means of the placenta, a development of the allantois. 
198 The Monotremes resemble Birds and Reptiles in having but one outlet 
for the rectum, genital, and urinary organs. They resemble Marsupials in 
having marsupial bones, but have no pouch. They differ from all other 
Mammals in having no distinct nipples. 
200 The pouch is wanting in some Opossums and the Dasyurus. 
201 The Edentates are allied to the Reptiles, especially the Tortoises: 
compare the carapax of the Armadillo, the broad ribs, toothless mouth, and 
gizzard-like stomach of the Ant-eater, and the great size of the blood-cor- 
puscles in the Sloth. 
