GLOSSARY-INDEX 407 



machine. Any mechanism designed to convert one kind of energy into 



another, 297. 

 macronucleus (Gr. macros = large). The larger of the two nuclei in cells 



having two, 62. 

 macrospore (Gr. macros large). The large spores ; n certain plants, 



which develop into female gametophytes, 122, 273. 

 macula lutea (Lat. macula = spot + luteus = yellow). A small spot on 



the retina, with most acute vision, 

 malaria, 69, 232. 



males. Individuals producing sperms, 251, 257. 

 male pronucleus. The sperm after entering the egg and before it unites 



with the egg nucleus, 257. 

 male spores, 122. 

 Malpighian bodies. Minute rounded bodies in the kidneys filled with a 



knot of blood vessels; glomeruli. 

 Mammalia (Lat. mamma = breast). Animals, the females of which have 



milk glands, 373. 



mammary glands. Glands secreting milk, 373. 

 mandible. The jaw bone, 180; also the jaw-like teeth of animals like 



insects and Crustacea. 



mantle. A fold of skin more or less enveloping the body of an animal, 

 marrow. The soft material filling the cavities of bones, 

 maturation (Lat. maturare = to make ripe). The final changes by which 



an egg becomes prepared for fertilization, 253. 

 maxilla. A bone forming the upper jaw, 180; also mouthparts of insects 



or Crustacea, 

 mechanical theory. The theory that life phenomena are manifestation? 



of chemical and mechanical forces only, 41. 

 medulla oblongata. The posterior part of the brain, 193. 

 medullary rays (Lat. medulla = marrow) . Bundles of cells extending from 



the center to the outer parts of a stem, 111. 

 Medusae. The sexual, free-swimming stage of certain hydroids and other 



Ccelenterata; jelly fishes, 144, 278. 

 megaspore. Same as macrospore. 



membrane bones. Bones formed first as membranes, 181. 

 membranella. A band of fused cilia found in some of the unicellular 



animals, 61. 



Mendelism. A law of heredity first advanced by Mendel, 359. 

 mental functions, 317. 



mesenteron (Gr. mesos = middle + enteron = intestine) . The mid-gut, 284. 

 mesentery (Gr. mesos = middle + enteron = intestine). A fold of the 



peritoneum which slings the intestine in position, 187. 



