GLOSSARY 567 



Manubrium (ma-nu'-bri-um), an extension down from the umbrella of the 



jellyfish. 

 Marine (ma-ren'), pertaining to things associated with the sea; salt water 



associations rather than fresh water associations. 

 Maxillary (max'-i-lar-l), pertaining to the upper jaw. 

 Medulla (me-dul'-a), the hind portion of the brain of chordates; the inner 



portion of the kidney; the inner portion of the adrenal glands. 

 Medusa (me-du'-sa), a stage in the life of jellyfish that somewhat resembles an 



umbrella. 

 Meiosis (mi-o'-sis), a special type of mitosis in which the chromosome number 



is halved. 

 Meroblastic (mer-o-blas'-tik), refers to an incomplete cleavage of the egg as is 



found in birds. 

 Mesenchyme (mes'-en-kim), wandering mesoderm cells. 

 Meso- (mes'-o), prefix meaning "middle". 



Mesoderm (mes'-o-durm), the middle germ layer of animal bodies. 

 Mesoglea (mes-o-gle'-a), a middle jelly-like layer found between the endoderm 



and ectoderm in the Coelenterata. 

 Mesonephros (mes-o-nef'-ros), the middle kidney, functional in the adult fish 



and amphibia. 

 Metabolism (me-tab'-o-lizm), a term referring to the building up of a store of 



potential energy in the cell and the release of this energy through oxidation. 

 Meta- (met'-a), prefix meaning "hind" or "posterior." 

 Metacarpal (met-a-car'-pal), a bone of the hand. 

 Metamorphosis (met-a-mor'-fo-sis), a transformation from one postembryonic 



stage to another in the life cycle of certain animals, such as insects. 

 Metanephros (met-a-nef'-ros), the hind kidney, found in adult reptiles, birds, 



and mammals. 

 Metaphase (met'-a-faz), the second phase of mitosis. 

 Metatarsal (met-a-tar'-sal), a foot bone. 

 Metazoa (met'-a-zo-a), animals with many cells in their bodies; animals not in 



the phylum Protozoa. 

 Micronucleus (mi'-kro-nu'-kle-us), the small nucleus found in Paramecium. 

 Mitosis (mi-to'-sis), the process of cell division in which chromosomes are 



formed and divided within the cell. 

 Molar (mo'-lar), grinding tooth; jaw tooth of mammals. 

 Molecule (mol'-e-kol), the smallest possible unit of matter that retains all of 



the properties of the matter; a molecule of water contains two atoms of 



hydrogen and one atom of oxygen and if further divided it loses the proper- 

 ties of water. 

 Molt (molt), a shedding of the outer covering of the body. 

 Morphology (mor-fol'-o-jl), a phase of biology dealing with structure of living 



organisms. 

 Morula (mor'-u-la), a stage of early cleavage of some vertebrates. 

 Mutation (mu-ta'-shun), a change in a gene that produces hereditary modifica- 

 tions in an organism. 

 Myotome (mi'-o-tom), a portion of the somite which develops into the large 



muscles of the vertebrate body. 



Naiad (na'-ad), an immature postembryonic stage in the life cycle of insects 

 with incomplete metamorphosis. 



