GLOSSARY 



503 



Metabolic, relating- to metabolism. 



Metabolism (Gk. m^tabole, change), the cycle 

 of chemical changes taking place within the 

 body. 



Metacarpale, pi. -ia, one of the skeletal ele- 

 ments supporting the palm. 



Metacarpus (Gk. ni^takarpiojiy the palm of 

 the hand), skeleton of palm of hand. 



Metamorphosis (Gk. for transformation), the 

 series of changes by which the adult stage is 

 attained, in cases where the young animal dif- 

 fers markedly from its parents. See Larva. 



Metatarsale, pi. -ia, one of the skeletal ele- 

 ments supporting the instep. 



Metatarsus (Gk. meta, after; tarsus, the broad 

 part of the foot), the skeleton of the instep- 

 region of the foot. 



Micronucleus (Gk. mikrils, small), in Ani- 

 malcules, the small nucleus. 



Microtome (Gk. mikros, small; fi^mnfi, I cut), 

 an instrument for cutting thin slices for 

 microscopic examination. 



Mid-gut, the middle section of the digestive 

 tube. 



Migration (L. migratio., removal from one 

 home to another), the wandering of species 

 from one place to another, often in a periodic 

 manner. See also Dispersal. 



Milk dentition, in Mammals, the first set of 

 teeth. 



Milk molar, in Mammals, one of the cheek- 

 teeth of the milk dentition. 



Mimicry, or Spurious warning, the resem- 

 blance existing between certain innocuous 

 forms and others exhibiting Warning- colora- 

 tion, &c. (which see). The mimicking species 

 share in the relative immunity enjoyed by the 

 mimicked forms. 



Miners' anaemia, a dangerous intestinal dis- 

 ease, caused by a palisade-worm (Dochmius 

 duodenalis). 



Molar, one of the permanent cheek-teeth of a 

 Mammal, belonging- to the hinder part of the 

 series, and without a predecessor in the first 

 set of teeth (milk teeth). 



Mongrel, a cross between two varieties or 

 races of the same species. Mongrels are 

 usually fertile. 



Morphology, (Gk. morphe, form ; Jugos, a 

 discourse), the study of form and structure. 



Morula (L. dim. of niorum, a mulberry), a 

 solid and spherical variety of Blastula 

 (which see). 



Mucous membrane, the soft membrane lining 

 the digestive tube. 



Mule, a cross between Horse and Ass. 



Muscle: (i) the tissue which makes up flesh; 

 (2) a definitely-shaped piece of flesh, con- 

 cerned with some special movement or move- 

 ments. 



Mutualism, or Symbiosis, the intimate associ- 

 ation of tw^o organisms as mutualists, for the 

 benefit of both. 



Myrmecophilous (Gk. myrmex, -ekos, an ant; 

 phileo, I love), of certain plants, protected 



by ants, which in return receive food and 

 shelter. 



Nagana, Fly-sickness (which see). 



Natural selection, the survival of individuals 

 which vary in favourable directions in rela- 

 tion to their surroundings. 



Nauplius (Gk. Nauplius, a son of Neptune), 

 in lower Crustaceans, an ovoid unsegmented 

 larva possessing only the three first pair of 

 head-appendages, by means of which it 

 swims. 



Nearctic region (Gk. n^^s, new; arktus, the 

 north), the northern part of the New World. 



Nectar (Gk. n'ikthr, the drink of the gods), a 

 sweet fluid produced by a nectary. 



Nectary, in plants, an organ secreting nectar. 



Neo-Lamarckism, a theory of evolution which 

 postulates the existence of definite Laws of 

 Growth. 



Neolithic period (Gk. n'SYjs, new; lithos, a 

 stone), the later stages of the Stone Age. 



Neotropical region (Gk. n^os, new; tr^pikus, 

 relating to the tropics). Central and South 

 America, with the West Indies. 



Nephridium, pi. -ia (dim. of Gk. iiephrSs, a 

 kidney), in many groups of animals, excre- 

 tory tulDes by which nitrogenous waste is 

 removed from the body. They place the 

 Coelom (which see) in communication with 

 the exterior. 



Neritic zone (nerites, a sea-snail), the shallow 

 waters of the sea. 



Nerve-cell, the essential part of a Neuron 

 (w'hich see). 



Nerve-fibre, the conducting thread into which 

 a Neuron (which see) is produced. 



Nerve-loop, in Molluscs, part of the central 

 nervous system which gives off nerves to the 

 gills and viscera. 



Nerve-ring, in Annelids, Arthropods, Molluscs, 

 &c., part of the central nervous system 

 which surrounds the front portion of the gut. 



Nervure, one of the linear thickenings support- 

 ing the wing of an Insect. 



Nettling-cell, in Zoophytes (Coelenterata), a 

 stinging capsule. 



Neural (Gk. n^iiriin, a nerve), related to the 

 central nervous system, or in the proximity 

 of this. 



Neuron (Gk. for a nerve), a nerve-unit, con- 

 sisting of a nerve-cell with its prolongations. 



Nictitating membrane, the translucent third 

 eyelid of Birds, &c., which can be drawn 

 over the eye as a protection. 



Nidicolse (L. nidus, a nest; colo, I inhabit), 

 in Birds, helpless nestlings. 



Nidifugae (L. nidus, a nest; fugio, I run 

 away), in Birds, young which run about and 

 feed themselves almost immediately after 

 hatching. 



Nitrifying, used of bacteria, &c., which cause 

 free nitrogen to enter into combination. 



Notochord (Gk. notSn, the back; chorde, a 

 string), an elastic supporting-rod which 



