GLOSSARY. 339 



MES-O-STER'NTTM (Gr. mesos, intermediate 5 sternon, the breast-bone). The 

 middle portion of the sternum, intervening between the attachment of the 

 second pair of ribs and the xiphoid cartilage (xiphisternum). 

 MES-O-THO'RAX (Gr. mesos; and thorax, the chest). The middle ring of the 

 thorax in Insects. 



MES-O-ZO'IC (Gr. mesos ; zoe, life). The Secondary period in Geology. 



MET-A-CAR'PUS (Gr. meta, after ; karpos, the wrist). The bones which form 

 the "root of the hand," and intervene between the wrist and the fingers. 



MET-A-MOR'PHO-SIS (Gr. meta, implying change ; morphe, shape}. ^ The changes 

 of form which certain animals undergo in passing from their younger to 

 their fully-grown condition. 



MET-A-PO'DI-UM (Gr. meta, after; pous. the foot). The posterior lobe of the 

 foot in Mollusca ; often called the " operculigerous lobe," because it de- 

 velops the operculum when this structure is present. 



ME-TAS'TO-MA (Gr. meta, after; stoma, mouth). The plate which closes the 

 mouth posteriorly in the Crustacea. 



MET-A-TAR'SUS (Gr. meta, after; tarsos, the instep). The bones which inter- 

 vene between the bones of the ankle (tarsus) and the digits in the hind-foot 

 of the higher Vertebrates. 



MET-A-THO'RAX (Gr. meta, after; thorax, the chest). The posterior ring of 

 the thorax in Insects. 



MI-MET'IO (Gr. mimetikos, imitative). Applied to organs or animals which 

 resemble each other in external appearance, but not in essential structure. 



MO'LARS (Lat. mola, a mill). The " grinders " in man, or the teeth in diphyo- 

 dont Mammals which are not preceded by milk-teeth. 



MOL-LUS'CA (Lat. mollis, soft). The sub-kingdom which includes the Shell- 

 fish proper, the Pblyzoa, the Tunicata, and the Lamp-shells ; so called from 

 the generally soft nature of their bodies. 



MOL-LUS-COI'DA (Mollusea ; Gr. eidos, form). The lower division of the Mol- 

 lusca, comprising the Polyzoa, Tunicata, and Brachiopoda. 



MON'ADS (Gr. monas, unity). Microscopical organisms of an extremely simple 

 character, developed in organic infusions. 



MO-NOC'U-LOUS (Gr. monos, single ; Lat. ooulus, eye). Possessed of only one 

 eye. 



MOX-O-DELPH'I-A (Gr. monos, single ; delphus, womb). The division of Mam- 

 malia, in which the uterus is single. 



MO-NCE'OI-OUS (Gr. monos, single ; oikos, house). Applied to individuals in 

 which the sexes are united. 



MON-O-MY'A-RY (Gr. monos, single ; mus, muscle). Applied to those bivalves 

 (Lamellibmnchiata) in which the shell is closed by a single adductor muscle. 



MON-O-PHY'O-DONT (Gr. monos ; phuo, I generate ; odpus, tooth). Applied to 

 those Mammals in which only a single set of teeth is ever developed. 



MOX-O-THAL'A-MOUS (Gr. monos / andthalamos, chamber). Possessing only a 

 single chamber. Applied to the shells of Foraminifera and Mollusca. 



MON-O-TREM'A-TA (Gr. monos ; trema, aperture). The order of Mammals com- 

 prising the Duck-mole and Echidna, in which the intestinal canal opens 

 into a " cloaca" common to the ducts of the urinary and generative organs. 



MUL-TI-LOC'U-LAR (Lat. multi, many ; loculus, a little purse). Divided into 

 many chambers. 



MUL'TI-VALVE. Applied to shells which are composed of many pieces. 



MUL-^TUN'GU-LA (Lat. multi, many; ungula, hoof). The division of Perisso- 

 dactyle Ungulates, in which each foot has more than a single hoof. 



MY'E-LON (Gr. muelos, marrow). The spinal cord of Vertebrates. 



MYR-I-AP'O-DA (Gr. murioi, ten thousand ; podes, feet). A class of Arthropoda 

 comprising the Centipedes and their allies, characterized by their numerous 

 feet. 



NA'CRE-OUS (Fr. nacre, mother-of-pearl, originally Oriental). Pearly ; of the 



texture of mother-of-pearl. 



NAT-A-TO'RES (Lat. nare, to swim). The order of the Swimming Birds. 

 NA'TA-TO-EY (Lat. nare, to swim). Formed for swimming. 



