Lepidosiren. An eel-shaped animal covered with rounded scales, having four rod-like members, and breathing water like a fish. It is found in ponds and rivers of intertropical Africa and South America. By some it is regarded as a fish, and by others as a batrachian.
Mammal. Belonging to the breast; from mamma, the breast or pap. An animal of the highest class of vertebrates, characterized by the female suckling its young.
Mammalia. The highest class of animals, including the ordinary hairy quadrupeds, the whales, and man, and characterized by the production of living young, which are nourished after birth by milk from the teats (mammæ, mammary glands) of the mother. A striking difference in embryonic development has led to the division of this class into two great groups: in one of these, when the embryo has attained a certain stage, a vascular connection, called the placenta, is formed between the embryo and the mother; in the other this is wanting, and the young are produced in a very incomplete state. The former, including the greater part of the class, are called placental mammals; the latter, or aplacental mammals, include the marsupials and monotremes (ornithorhynchus).
Marsupials. An order of Mammalia in which the young are born in a very incomplete state of development, and carried by the mother, while sucking, in a ventral pouch (marsupium), such as the kangaroos, opossums, etc. (see Mammalia).
Molecule. A mass; one of the invisible particles supposed to constitute matter of any kind.
Mollusk. An invertebrate animal, having a soft, fleshy body (whence the name), which is inarticulate, and not radiate internally.
Monkey. See Simia.
Monogamy. A marriage to one wife only, or the state of such as are restricted to a single wife, or may not marry again after the death of a first wife.
Monotheism. The doctrine or belief that there is but one God.