340 Glossary 



Mon-o-hy'-brid. The offspring of parents differing in one character. 

 Mon'-o-tremes. The lowest group of mammals, including the duck-bill 



and the spiny anteater. 

 Mor-phol'-o-gy. The science which deals with structure and form. 

 Mus'-ca. A genus of flies including the house-fly. 

 Mu'-tant. A sudden variation or sport which breeds true. 

 Mu-ta'-tions. Inherited variations which are more or less striking; 



"sudden variations," "sports." 

 Nec-tu'-rus. A large salamander ; the mud-puppy. 

 Nem'-a-tode. A round-worm or thread-worm. 

 Ne'-re-is. A marine annelid, or ringed worm. 

 Neural Groove. The groove on the dorsal surface of the embryo of a 



vertebrate which develops into the brain and spinal cord. 

 Neural Tube. A tube formed from the neural groove and giving rise to 



brain and spinal cord. 

 No'-to-chord. The cellular rod which forms the basis of the backbone. 

 Nu'-cle-us. The central organ of a cell, composed of chromatin and 



achromatin. 

 Nulliplex Factors or Character. A condition in which a character is 



absent because its determiner is found in neither parent. 

 On-tog'-e-ny. Development of an individual. 

 O'-o-cyte. The ovarian egg before maturation (formation of polar 



bodies). 

 O-o-gen'-e-sis. The development of an ovum from a primitive sex-cell. 

 O-o-go'-ni-a. The earliest generations of cells which produce ova; pri- 

 mordial egg cells. 

 O'-o-sperm. The fertilized egg after union of egg and sperm. 

 Order. The chief sub-division of a class. 

 Organization. Differentiation and integration, i.e., different parts united 



into one whole. 

 Or-gan-og'-e-ny. The formation of various organs of the body. 

 Or-tho-gen'-e-s:s. The doctrine that the course of evolution is definitely 



directed by intrinsic causes. 

 O-vi-par'-i-ty. Young brought forth as eggs, i.e., in an early stage of 



development. 

 O'-vules. The female sex cells of flowering plants with the immediately 



surrounding parts. 

 O'-vum. The female sex cell. 

 Ox-y-chro'-ma-tin. That portion of the chromatin which does not form 



chromosomes., 

 Pan-gen'-e-sis. The hypothesis proposed by Darwin that every cell of the 



body gives off minute germs, "gemmules," which then collect in the 



sex cells 



