446 CHORDATE ANATOMY 



monocytes. Large mononuclear leucocytes with kidney-shaped nuclei. 

 monoecious. Having male and female flowers separated on the same plant. 

 monophyletic theory. The theory that all forms of blood cells arise from a common 



primitive type of cell or hemoblast. 

 monophyodont. Having a single permanent set of teeth. 

 monorhine. Having a single narial aperture. 



monosaccharid. A sugar the molecules of which have only six carbon atoms. 

 mons pubis. The pubic eminence or mons veneris. 



morphology. The science which treats of form and structure of organisms. 

 morula. The mulberry stage of segmentation of the egg. 

 motor (efferent) neuron. A nerve cell which conveys impulses away from a nervous 



center. 

 mucosa. The lining of the intestine. 

 Muellerian duct. The oviduct or uterine tube. 

 multitubercular. Having many cusps as the molar teeth do. 

 muscularis mucosae. The layer of smooth muscle fibers in the mucosa. 

 myelencephalon. The fifth or posterior division of the brain — the medulla oblongata. 

 myelin. The fat-like substance which forms the Schwann's sheath of nerve fibers. 

 myelocytes. Cells of red bone marrow usually with granular cytoplasm. 

 myenteric plexus. The network of sympathetic fibers on the muscles of intestine. 

 myocardium. The muscular layer of the heart. 

 myocoele. The coelom of the somite. 



myocomma. The connective tissue between two myotomes. 

 myofibril. One of the fine fibrils within a muscle fiber. 

 myotome. The muscular portion of a somite. 

 myxine. The hagfish, a genus of cyclostomes. 



nail wall. The skin which covers the base of the nail. 



nares. The nostrils. 



navicular. The scaphoid bone of the carpus and tarsus. 



Neanderthal. A gorilla-like type of fossil man. 



necrobiotic. Dying as a result of functional activity. 



neocortex. The major portion of the cerebral hemispheres. 



neostoma. The definitive mouth of vertebrates. 



neostriatum. An olfactory center, near the corpus striatum, which becomes in mammals 



the nucleus amygdalae. 

 nephridiimi. The ectodermal excretory tubule of annelids and amphioxus. 

 nephrostome. The opening of a nephridium into the body cavity. 

 nephrotome. The intermediate portion of the mesodermal somite which gives rise to 



a renal tubule. 

 nerve. A bundle of nerve fibers which connect the central nervous system with some 



part of the body. 

 nerve fiber. The axon process of a neuron plus sheaths when such occur. 

 nerve nucleus (nidulus). A group of nerve cells within the central nervous system. 

 nerve tract. A bundle of nerve fibers of similar origin and function within the central 



nervous system. 

 nervus terminalis. A sensory nerve associated with the olfactory." 

 neuraxon. The nerve fiber or axon process of a nerve cell. 

 neurenteric canal. The blastoporic opening which in chordate embryos connects the 



neural tube with the enteron at the posterior end of the body. 

 neurolemma. 'J'he cellular sheath of an axon. 

 neurite. The axon process of a neuron which carries impulses away from the cell body. 



