34 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-SIS. 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. 



