590 GLOSSARY. 



MONOECIOUS (Gr. monos, single ; oikos, house). Applied to individuals in 

 which the sexes are united. 



MONOMYARY (Gr. monos, single ; muon, muscle). Applied to those bivalves 

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



MONOPHYODONT (Gr. motios ; phuo, I generate; odous, tooth). Applied to 

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



MONOTHALAMOUS (Gr. monos ; and thalamos, chamber). Possessing only a 

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



MONOTREMATA (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. 



MULTILOCULAR (Lat. multus, many; loculus, a little purse). Divided into 

 many chambers. 



MULTIVALVE. Applied to shells which are composed of many pieces. 



MULTDNGULA (Lat. multus, many ; ungula, hoof). The division of Perisso- 

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



MYELON (Gr. muelos, marrow). The spinal cord of Vertebrates. 



MYRIAPODA (Gr. murios, ten thousand ; poda, feet). A class of A rthropoda 

 comprising the Centipedes and their allies, characterised by their numer- 

 ous feet. 



NACREOUS (Fr. nacre, mother-of-pearl, originally Oriental). Pearly, of the 

 texture of mother-of-pearl. 



NATATORES (Lat. nare, to swim). The order of the Swimming birds. 



NATATORY (Lat. nare, to swim). Formed for swimming. 



NAUTILOID. Resembling the shell of the Nautilus in shape. 



NECTOCALYX (Gr. necho, I swim; kalux, cup). The swimming-bell or "disc" 

 of a Medusa or Jelly-fish. 



NEMATELMIA (Gr. nema, thread ; helmins, a worm). The division of Scolecida 

 comprising the Round-worms, Thread-worms, &c. 



NEMATOCYSTS (Gr. nema, thread ; kustis, a bag). The thread-cells of the Cce- 

 lenterata . (See Cnid SK) . 



NEMATOIDEA (Gr. nema, thread ; eidos, form). An order of Scolecida compris- 

 ing the Thread-worms, Vinegar-eels, &c. 



NEMATOPHORES (Gr. nema, thread ; phero, I carry). Csecal processes found 

 on the co3nosarc of certain of the Sertularida, containing numerous thread- 

 cells at their extremities. 



NEMERTIDA (Gr. Nemertes, proper name). A division of the Turbellarian 

 Worms, commonly called "Ribbon- worms." 



NERVURES (Lat. nervus, a sinew). The ribs which support the membranous 

 wings of insects. 



NEURAL (Gr. neuron, a nerve). Connected with the nervous system. 



NEURAPOPHYSIS (Gr. neuron, a nerve ; apophusis, a projecting part). The 

 " spinous process " of a vertebra, or the process formed at the point of junc- 

 tion of the neural arches. 



NEUROPODIUM (Gr. neuron, a. nerve ; pous, the foot). The ventral or inferior 

 division of the "foot-tubercle" of an Annelide ; often called the "ventral 

 oar." 



NEUROPTERA (Gr. neuron; and pteron, a wing). An order of Insects charac- 

 terised by four membranous wings with numerous reticulated nervures 

 (e.g., Dragon-flies). 



NEUTER (Lat. neither the one nor the other). Having no fully developed sex. 



NIDIFICATION (Lat. nidus, a nest ; facio, I make). The building of a nest. 



NOCTURNAL (Lat. nox, night). Applied to animals which are active by night. 



NORMAL (Lat. norma, a rule). Conforming to the ordinary standard. 



NOTOBRANCHIATA (Gr. notos, the back ; and bragchia, gill). Carrying the gills 

 upon the back ; applied to a division of the Annelida. 



NOTOCHORD (Gr. notos, back ; chorde, string). A cellular rod which is devel- 

 oped in the embryo of Vertebrates immediately beneath the spinal cord, 

 and which is usually replaced in the adult by the vertebral column. Often 

 it is spoken of as the "chorda dorsalis." 



