Appendix 841 



Macromere (mak'romere) (Gr. makros, large; meros, part), large cells pro- 

 duced by embryonic cleavage in certain organisms. 

 Macronucleus (mak ro nu' kle us) (Gr. makros, large; L. nucleus, nucleus), the 



larger nutritive nucleus of certain protozoa as distinguished from the 



smaller reproductive micronucleus. 

 Macrophyll (mak'rofil) (Gr. makros, large; phyllon, leaf), large leaf (same as 



Megaphyllous). 

 Macroscopic (mak ro -skop' ik) (Gr. makros, large; skopein, to see), visible to the 



naked eye. 

 Macrospore (mak' ro spor) (Gr. makros, large; spora, spore), the larger spore 



of a heterosporous plant. 

 Madreporite (mad' re po rit) (L. mater, mother; Gr. poros, porous), porous plate 



leading to the water — vascular system of a starfish. 

 Malaria (ma -la' ri a) (L. mal, bad; aria, air), fever produced by Protozoa (class 



Sporozoa), formerly thought due to "bad" air. 

 Malpighian (mal -pig' i an) (after Malpighi, of Pisa), malpighian corpuscle is a 



body in a vertebrate kidney {see Bowman's capsule). 

 Mammal (mam'al) (L. mamma, breast), vertebrates having milk-giving breasts. 

 Mandible (man' di bl) (L. mandere, to chew), chewing jaw. 

 Mantle (man'tl) (L. mantellum, cloak), sheethke tissue in clams, oysters, snails 



to secrete shell. 

 Marsupial (mar -sup' i al) (L. marsupium, pouch), mammals that carry young in 



an abdominal pouch as opossum, kangaroo, etc. 

 Mastax (mas' taks) (Gr. mastax, mouth), crushing apparatus in rotifers. 

 Matrix (ma' triks) (L. ?nater, mother), noncellular material in which cells are 



embedded, as in cartilage, bone, etc. 

 Maturation (mat u -ra' shun) (L. maturus, mature), m.aturing of sperm or eggs. 

 Maxilla (maks -il' a) (L. maxilla, jaw), a jaw, especially the upper in higher 



animals. 

 Maxilliped (maks -il' i ped) (L. maxilla, jaw; pes, foot), an appendage modified 



to serve as a masticatory organ and foot; the three pairs of appendages 



of a crayfish thorax just posterior to the maxillae. 

 Mechanism (mechanistic view), theory (in contrast to Vitalism) that states that 



life can be explained in terms of natural transformations of energy and 



matter without the introduction of any immaterial or extranatural "vital 



forces." 

 Medulla (me -dul' la) (L. medulla, marrow), inner portion of an organ as the 



medulla of the kidney. Medulla oblongata is the posterior part of the 



brain. 

 Medullary plate, groove, and tube, three successive stages in the embryologic 



development of the central nervous system of vertebrates. 

 Medullary ray, pith ray that separates the vascular bundles in certain higher 



plants. 

 Medullary sheath, covering of a medullated nerve fiber. 

 Medusa (me -du' sa) (Gr. medousa, one who rules), free-swimming hybroid 



(jellyfish). 



