INDEX 



419 



Mesentery, 80, 205 



Mesoderm, in embryo, 205, 206, 207, 208, 

 209, 210, 211, 212 



organs from, 207 

 Mesohippus, 340 



feet of, 341 



skull of, 341 



tooth of, 340 

 Mesozoa, 275 

 Mesozoic, 330, 335 

 Metabolism, 46-50 

 Metacarpals, 93 

 Metagenesis, 173, 174 

 Metamere, 79, 80 

 Metamerism, 79 

 Metamorphosis, 192, 214, 215 

 Metaphase, 56, 57, 60 

 Metatarsals, 93 

 Metazoa, evolution of, 64-76 



sexual reproduction in, 160, 161 

 Metazoan individual, as distinguished 



from colon.y, 74, 75 

 Microgromia, gregaloid colony in, 67 

 Micronucleus, 162, 163 

 Micropyle, 199 

 Microscope, 9, 10-11, 14, 19 

 Microtus, outbreaks of, 319, 320 

 Migration, normal, 317 



periodic, 318 * 



sporadic, 319, 320 

 Miocene, 330, 335 

 Mirbel, 15 



Mississippian, 330, 332, 335 

 Mitochondria, 26, 27 

 Mitosis, 55-62 



genetic significance of, 62, 63 

 Moeritherium, 335, 336, 337, 339 

 Moisture, ecological relations of, 285-287 



effect of, on reactions, 286 

 Mold, a fossil, 326, 327 

 Molecule, 30 

 Mollusca, 270-272 

 Monoecious, 166 

 Monosaccharide, 40 

 Morgan, T. H., 19 



genetic studies of, 355 

 Morphology, 20, 22 

 Motor neuron, 145 

 Motor unit, 96 

 Mouth, of earthworm, 101 



of flatworm, 102 



Mouth, of frog, 102, 103 



of Hydra, 71, 72 



of mammal, 101 

 Muscle, 93, 94, 95 



cardiac, 94, 96 



chemistry of contraction of, 98, 99 



contraction of, 96-99 



efficiency of, 98 



fatigue of, 96, 99 



involuntary, 96 



opposing sets of, 93, 94 



smooth, 94 



striated, 94, 95 



voluntary, 96 

 Muscle twitch, diagram of, 96 

 Mutation, 238, 353-357 



causes of, 356, 357 



direction of, 359 

 Myehn sheath, 143, 146, 148 

 Myofibril, 95 

 Myosin, 99 

 Myotome, 205 

 Myriapoda, 272, 274 

 Mysis, 256 



N 



Natural selection, 360-363 



criterion of advantage in, 362, 365 

 Nauplius, 256 

 Nautiloid, suture of, 343 

 Neanderthal man, 345, 346 



flints used by, 346 

 Nectocalyx, 174, 175 

 Nemathelminthes, 266, 267 

 Nematocyst, of Hydra, 72 

 Nematomorpha, 275 

 Nemertinea, 275 

 Nephridiopore, 135 

 Nephridium, 135 

 Nephrostome, 135, 136 

 Nerve, 141, 146 

 Nerve impulse, 148, 149, 150 

 Nervous system, 140-152 



autonomic, 143 



central, 142 



diagrams of, 142 



in embryo, 207, 208, 212 



induced by notochord, 219 



peripheral, 142, 143 



rise of, 140-142 



