INDEX — GLOSSARY 



433 



Mesentery (plu. mesenteries), 123, 124, 

 126. 



Mesoderm, the layer of cells between 

 the endoderm and ectoderm in the 

 embryo of all animals above the 

 ccelenterates. It is composed of cells, 

 as are the other two layers, and is 

 probably developed from both of 

 these. 



Mesoglcea, the middle of the three 

 body layers in the sponges and 

 ccelenterates. It may be gelatinous 

 (without cells) or cellular ; but always 

 differs from mesoderm (the middle 

 layer of higher animals) in being 

 derived from the endoderm or ecto- 

 derm comparatively late in life and not 

 developed from a third embr>'onic 

 layer (the mesoblast) ; of ccelenterates, 

 108 ; of corals, 126 ; of Hydrozoa, 1 1 1 ; 

 of sponges, gg, qq, ioi. 



Mesohippus, 393, 3Q3, 3Q4, jqs. 



Mesonyx, 3g7. 



Mesozoic, 407. 



Metacarpal bones, of birds, 370, 372 ; 

 of cat, 325, 327, 327; of mammals, 



325, 327, 327, 385, 326, 395; of 

 reptiles, 366, 367. 



Metacarpus, the palm {327) ; see meta- 

 carpal bones. 



Metamorphosis, example of among 

 insects, 317 ; in the house fly, 317. 



Metastome, in crustaceans, 280, 2S6, 

 287. 



Metatarsal bones, of cat, 327, 328; 

 of mammals, 383 ; of reptiles, 366, 367. 



Metatheria, 378; production of young, 



377- 



Metazoa, includes practically all ani- 

 mals above the Protozoa. 



Metridium marginatum, 134. 



Mice, 381, 382. 



Microcyclas, 131 ; M. discus, 131. 



Migration, cause of, in birds, 370; of 

 animals, 23, 24 ; of elephant, 23 ; of 

 Littorina littorea, 23, 24 ; of mammals, 

 23; of Trinucleus, 23. 



Mildev.^s, 40. 



Milk, of mammals, 374; secretion of, 

 335. 



Milk teeth, 331. 



Millepora, 121. 



Millipedes, 309. 



Miocene, 407. 



Miocene fossils figured, 34, 76, 03, 223, 

 245, 251, 31 Q, 342, 388, 393, 304, 395. 



Miohippus, 393, 3g4. 



Missing links, examples of, in arachnid 

 evolution, 310, 314; in the scorpions, 

 310. 



Mississippian, 407. 



Mi.ssissippian fossils figured, 158, 170, 

 180, 188, 265. 



Mites, 316. 



Mixosaurus, 35g. 



Mixotermitoidea, 318. 



Modern man, 400. 



Mceritherium, 387, 388; in evolution, 

 398. 



Molar tooth, cement of, 387 ; enamel of, 

 387 ; how distinguished, 374 ; ivory 

 (dentine) of, 387; of cat, 331; of 

 Eohippus, 393; of Equus, 393; of 

 Hyracotherium, 393 ; of Mesohippus, 

 393 ; of Protohippus, 393 ; of Pro- 

 torohippus, 393. 



Molds, 14, 14; external, giving former 

 shape of organism, 16; external, of 

 shells, 14 ; external, of skin, 19 ; 

 internal, of shells, 14, 1 5, 246 ; internal, 

 of sponge, 104. 



Molds (plants), 40. 



Molecular replacement in fossils, 11, 12. 



Moles, 37g ; habitat of, 374. 



MoUusca, see moUusks, 206-273. 



Molluscoidea, 173-205; see under 

 Bryozoa and Brachiopoda ; geologic 

 range of, 4og. 



MoUusks, 206-273 ; circulatory system, 

 206 ; classification of, 207 ; develop- 

 ment of, 207 ; digestive system, 206 ; 

 excretory system, 207 ; food of squids, 

 270; fossils, see under the classes of; 

 geologic range of, 4og ; in evolution, 

 83 ; nervous system, 207 ; respiration 

 in, 206 ; sexes of, 207 ; shell gland in, 

 207. 



Molting, 277, 278; cause of, 277; in 

 the crayfish, 277 ; in the horseshoe 

 crab, 277 ; times of, 277. 



Monactinellida, g7, g8, 106. 



Monkeys, broad nostril, 3gg ; capuchins, 

 3gg; habitat of, 374; howling, 39g ; 

 narrow nostril, 3gg ; new world, 3gg; 



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