embryo of the whale-bone whales. They vary in number, from one in the narwhal* to 190 in the dolphin.

The Alimentary Canal consists of the following parts:—

Salivary glands exist throughout the whole Mammalian class (except in the Cetacea), and follow closely the type presented in the human race; in the ant-eater they are greatly developed, and pour their secretion into a special reservoir, called a salivary bladder. There are three distinct forms of stomach seen in this class, viz., simple, compound, and complex. The simple stomach consists of a single cavity, and is met with in Bimana, Quadrumana, Carnivora, and in some of the Cheiroptera, Insectivora, Edentata, Cetacea, Marsupialia, and Monotremata. The compound stomach is a variety of the former, consisting of a single cavity partially divided by folds into two or more spaces; this form of stomach is seen in the Carnivorous Cetacea, Sloths, a few of the Rodents, and some others. The complex stomach is the most interesting of all, and is met with only among the Ruminants; it consists of four cavities, named as follows:—

a Paunch, Rumen, or Ingluvies.

b. Reticulum, or Honeycomb.
c. Omasum, Manyplies, or Psalterium.
d. Abomasum, or Rennet.

* The narwhal has a second tooth, but it is rudimentary.

The Liver is the largest gland in the bodies of most animals, and performs a double function—that of elaborating a secretion necessary for digestion, and eliminating an excretion of hydro-carbons from the blood. The Kidneys are situated in the lumbar region, and are principally engaged in eliminating from the blood nitrogen, in the form of urea.

RESPIRATION.-All Mammals breathe by means of lungs, which are divided into lobes (except in the horse, elephant, and some of the mutilata); the inspired air is warmed to the temperature of the animal, and robbed of oxygen, while the expired air is charged with carbonic acid gas, watery vapour, and a minute quantity of organic matter. The peculiar respiration of the Cetacea will be described in another place.

CIRCULATION. The Heart consists of four chambers, and the blood contains non-nucleated red corpuscles, which are circular (except in the camel tribe, in which they are oval). The thoracic cavity is always separated from the abdominal by a muscular partition, termed the diaphragm or midriff.

NERVOUS SYSTEM. The encephalon in man has reached its maximum of development, and is much more complete and intricate in its formation than in the most sagacious of the other Mammals; as we descend through the different orders, we shall find it more simplified, the convolutions become less intricate, and gradually disappear, until we arrive at the Marsupialia and Monotremata, where we find the corpus callosum wanting. (See Owen's classification, postea.) In the same ratio the intellectual faculties decrease. In all Mammalia the cerebral hemispheres (prosencephala) overlap the olfactory lobes (rhinencephala) in front, and the optic lobes (mesencephala)—usually called corpora quadra

gemina (for they are no longer bigeminal) behind. The pons Varolii is always present, and the cerebellum has lateral lobes in addition to a median one.

SENSES. The sense of taste is believed to exist in all Mammalia, except the Cetacea. The sense of touch is possessed by all Mammals, but in some it is more highly developed than in others. All Mammals have the sense of smell, except Cetacea; while those who possess it in a marked degree, such as the dog, have the turbinated bones extremely convoluted-hence termed the "labyrinth,"-for the purpose of increasing the sentient surface. The sense of hearing is universally present, and the formation of the middle and internal ear is very nearly similar throughout the entire class: the three ossicula always exist in the tympanum, while the cochlea, semicircular canals, and vestibule are invariably present; but the pinna and external auditory meatus are absent in the armadillos, moles, duck-moles, seals, and Cetacea. Those animals that have this sense very acute, like the bats, possess large pinnæ. The sense of sight exists throughout the entire class, except in the adult mole (in the young mole the eye is well developed). The coats and dioptric media of the eye are similar to those of man. All have lacrymal glands and eyelids, except the Cetacea, while in these the sclerotic coat is greatly thickened, as in fishes. There is situated at the inner canthus of the eye of Ruminants a gland, called the Harderian gland, for the purpose of assisting to lubricate the eyeball. Nearly all Mammals (with the exception of man, monkeys, the Edentata and Monotremata) have that peculiar membrane called tapetum lucidum in their eyes; it is this membrane that gives to a cat's eyes in a dark room the peculiar lustre so familiar to every one. Various classifications of the Mammalia have been proposed. I have arranged in a tabulated form the three principal classifications now most generally adopted.

CHAPTER III.

MAMMALIA: ORDERS.

I. BIMANA contains only one genus and one species, homo. Man was formerly placed along with the Quadrumana in the order Primates by Linnæus and some other naturalists, but has now assigned to him a distinct order, in consequence of the many striking differences which exist between him and the gorilla, the most anthropoid of all Quadrumana: Professor Owen enumerates no less than thirty in the cranium alone. The following are the most important distinguishing characteristics of this order: The possession of moral and reasoning faculties, the greater comparative development of the brain, the summit of the teeth form almost a perfect level, and are not separated from each other by any interval. The dental formula is—

The great toe is not opposable to the other digits, the foot is plantigrade, the arms are shorter than the legs, and are never used as instruments of locomotion; the body is

erect.

The human family is, according to Blumenbach, composed of the following five races (Cuvier originally described the first three groups) ::

1. Caucasian includes all Europeans (except Finns), the natives of Western Asia and Northern Africa. They possess the following characters—an orthognathous (open, straight, and yvάoos, jaw) cranium, an elliptical or oval skull, wellformed forehead, small face, narrow medium-sized nose, thin lips, and prominent rounded chin; Camper's facial angle measures from 80° to 85°; their hair is soft and wavy, never crisp, and their skin is fair, or slightly brown.