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. 



