GLOSSARY. 381 



Median. Having reference to the middle line of the body. 



Medulla oblongata. The oblong medullary column at the base of the brain, from 

 which the spinal chord or marrow is continued. 



Medus.i;. a genus or family of soft radiated animals or acalephes, so called because 

 their organs of motion and prehension are spread out like the snaky hair of the 

 fabulous Medusa. 



Mesentery. (Gr. rnesos, intermediate ; and enterosy entrail.) The membrane 

 which forms the medium of connection between the small intestines and the 

 abdomen. 



Mesogastric. {Gv.mesos; and ^as/er, stomach.) The membrane which forms the 

 medium of attachment of the stomach to the walls of the abdomen. 



Mesonotum. {Gy. mesos, middle; notos, back.) The middle piece of that half of 

 the segment which covers the back. 



Mesosternum. ( Gr. mesos ; sternon, the breast.) The middle part of that half of 

 the segment which covers the bi'east. 



Mesothorax. {Gr. mesos, middle; and thorax, the chest.) The intermediate of 

 the three segments which form the thorax in insects. 



Metathorax. {Gv.meta, after; thorax.) The hindmost of the three segments 

 which compose the thorax of an insect. 



Miocene. (Gr. vhcw??, less ; /?amos, recent.) The tertiary epoch in which a mi- 

 nority of fossil shells are of the recent species. 



Molecules. (Dim. of moZe^, a mass.) Microscopic particles. 



Mollusca. (Lat. mollis, soft.) The primary division of the Animal Kingdom, 

 characterised at page 13. 



Monad. (Gr. mn7ias, unity.) The genus of the most minute and simple micro- 

 scopic animalcules, and shaped like spherical cells. Monadiform, like a monad. 



Monoculus. (Gr. monos, single; Lat. ocuhts, an eye.) The animals which have 

 but one eye. 



Monomvary. (Gr. monos, single; inuon, a muscle.) A bivalve whose shell is 

 closed by one adductor muscle. 



Monothalamous. {Gr. monos ; thalamos, a chamber.) A shell forming a single 

 chamber, like that of the whelk. 



Morphological. ( Gr. morphe, form ; logos, a discourse. ) The history of the mo- 

 difications of form which the same organ undergoes in different animals. 



Motory. The nerves which control motion. 



Multivalve. (Lat. multus, many; valvce, folding-doors.) Shells composed of 

 many pieces or valves. 



IMyelexcephala. {Gr. muelos, marrow; egkephalon, brain.) The primary divi- 

 sion of animals characterised by a brain and spinal marrow. 



IVIyriapoda. { Gr. murios, ten thousand; pous, foot.) The order of insects cha- 

 racterised by their numerous feet. 



Nacreous. Pearly, like mother-of-pearl. 



Natatory. An animal or part formed for swimming. 



Nematoidea. (Gr. nema, a thread ; eidos, like.) The intestinal worms, which are 



long, slender and cylindrical like threads. 

 Nematoneura. (Gr. 7iema, a thread ; neuron, a nerve.) The animals in which 



the nervous system is filamentary, as in the star-fish. 

 Nervures. (Lat. nervus, a sinew.) The delicate frame- work of the membranous 



wings of insects. 

 Neurilemjia. ( Gr. neuron, anerve ; lemma, a covering. ) The membrane which sur- 

 rounds the nervous fibre. 

 Neurology (Gr. neuron a nerve ; logos, a discourse.) The science of the nervous 



system. 

 Neuroptera. {Gr. neuron, a nerve; pteron, a wing.) The order of insects with 



four wings, characterised by their numerous nervures, like those of the dragon-fly. 

 Nidamental. (Lat. nidus, a nest.) Relating to the protection of the egg and 



young, especially applied to the organs that secrete the material of which many 



animals construct their nests. 

 Nodule. (Dim of nodus, a knot.) A little knot-like eminence. 

 Normal. (Lat. norma, rule.) According to rule, ordinary or natural. 



