Glossary 337 



"CROSS-OVERS." The regrouping of linked characters, probably caused 

 by interchange of genes between bivalent chromosomes. 



CTEN'-O-PHORE. A jelly-sphere; a member of a phylum of marine animals 

 standing above the jelly-fishes. 



CY-CLO'-PI-A. A monstrosity in which both eyes have fused into a single 

 one. 



CY-TOL'-O-GY. The science which treats of cells. 



CY'-TO-PLASM. The protoplasm of a cell outside of the nucleus. 



DAL'-TON-:SM. That form of color-blindness in which one is unable to dis- 

 tinguish red and green ; usually limited to males. 



DAR'-WIN-ISM. The doctrine that evolution takes place through natural 

 selection or the survival of the fittest. 



DETERMINANTS. The units of heredity (Weismann). 



DETERMINER. The differential cause or factor in a germ cell which deter- 

 mines the development of a character. 



DEX'-TRAL SNAIL. The usual type of snail in which the shell coils from 

 base to apex in a clockwise direction. 



DIFFERENTIATION. The process of producing specific parts or substances 

 from a general part or substance. 



DI-HY'-BRID. The offspring of parents differing in two characters. 



DI-O-NAE'-A. An insect-catching plant, the "Venus Fly-trap." 



DIP'-LOID. The full number of chromosomes found in the fertilized egg 

 and in all cells derived from this, except the mature germ cells. 



DOMINANT CHARACTER. A character inherited from one parent which de- 

 velops to the exclusion of a contrasting character of the other parent. 



DROS-OPH'-I-LA. A genus of fruit-flies. 



DU'-PLEX FACTORS or CHARACTER. A condition where the determiners for 

 a character are derived from both parents. 



E-CHI'-NO-DERMS. A phylum of marine animals which includes star-fishes 

 and sea-urchins. 



E-COL'-O-GY. The science which deals with the relations of organisms to 

 one another and to environment. 



EC'-TO-DERM. The outer layer of cells of an embryo which gives rise to 

 epidermis, sense organs and nervous system. 



EM-BRY-OG'-E-NY. Early development of an egg leading to the formation 

 of an embryo. 



EN'-DO-DERM. The inner layer of cells of an embryo, which gives rise to 

 the digestive cells of the alimentary system. 



EN-DO-GEN'E-SIS (= development from within). The theory that the 

 differential causes of development are within the germ cells, which 

 are therefore complex. 



