388 PRINCIPLES OF ANIMAL BIOLOGY 



Marsupial {mar su' pi al). A mammal having a pouch in which the young are carried 

 (for example, the opossum and the kangaroo). As an adjective, possessing a pouch ; 

 as the marsupial frog. 



Mastigophora {man' ti gof o ra). A class of Protozoa, characterized by flagella. 



Mastodon {mas' to don). An extinct genus of elephant-like animals of Phocene and 

 Pleistocene time. 



Maternal {ma ter' nal). Pertaining to or derived from the mother. 



Matrix {ma' triks). The non-cellular material in which the cells of bone and cartilage 

 are imbedded. 



Maturation {mat' ura' shun). A process which germ cells undergo before they be- 

 come functional, consisting essentially of (usually) two cell divisions, in at least 

 one of which the behavior of the chromosomes is unlike that in other cell divisions. 



Medulla oblongata {me duV la oh' long go' ta). The enlargement of the anterior end 

 of the spinal cord in vertebrates, commonly regarded as the posterior division of 

 the brain. 



Medusa {me du' so) {pi., medusae, tnedu' see). A jellyfish; the free-swimming 

 member of many hydroid species. 



Megapodes {meg' a po' deez). Birds of the family Megapodiidae, the mound-birds 



and jungle fowls. 

 Mendel, Gregor {men' del). Austrian monk and plant breeder, founder of modern 



movement in genetics, and author of "Mendel's Law" of heredity. Lived 1822- 



1884. 

 Mendel's Law {men' delz law'). The law that genes for inherited characters separate 



from one another and recombine in various ways in the germ cells. 



Meridional (me rid' i o nal). Passing through the animal and vegetative poles; 

 said of certain cleavage planes of an egg. 



Merozoite {mer' o zo' He). One of a number of minute motile cells formed by mutliple 

 division of the nucleus and subsequent fragmentation of the cytoplasm of the cells 

 of Coccidium and similar parasites, while in the intestinal cells of the host. 



Merychippus {mer' i kip' pus). An extinct horse-like animal of Miocene time. 



Mesentery (?«es' en ter i). A double sheet of tissue, continuous with the peritoneum, 



which supports an organ (such as the intestine) from the body wall. 

 Mesoderm {mes' o derm). A layer of cells between the ectoderm and endoderm. 

 Mesohippus {mes' a hip' pus). An extinct animal of Oligocene time, ancestral to the 



horse. 

 Mesozoa {mes' o zo' a). A group of degenerate animals of uncertain rank and rela- 

 tionship, once regarded as intermediate between Protozoa and metazoa, hence the 



name. 

 Mesozoic {mes' o so' ik). Pertaining to the geological era between the Paleozoic and 



Cenozoic, or the age of reptiles. 

 Metabolism {me tab' o liz'm). The sum total of the chemical processes going on in 



protoplasm. 

 Metacarpal {met' a kar' pal). One of the bones forming the body of the hand or fore 



foot in vertebrates. 

 Metagenesis {met' a jen' e sis) . The occurrence of two or more forms of individual 



in the same species, one or more of which reproduce asexually and one of which 



reproduces sexually. 

 Metamere {met' a meer). See somite. 



