GLOSSARY 521 



Cho'-ri-on. A tough membrane around an egg secreted by 



surrounding cells. 

 Chro'-ma-tin. The deeply staining substance of the nucleus. 

 Chro'-mo-somes. Deeply staining bodies found in the nucleus 



at the time of indirect division. 

 Cil'-i-a. Minute protoplasmic threads on the surface of a cell 



which produce movements in the surrounding medium by 



waving back and forth. 

 Class. The chief sub-division of a phylum. 

 Cleav'-age. The division of the egg cell after fertilization into 



many cells. 

 Clep-si'-ne. A genus of leeches. 

 Coe'-lom. The body cavity. 



Continuous variation. A series of minute variations. 

 Correlative differentiation. Differentiation due chiefly to 



the interaction of different parts of an organism. 

 Cre-pid'-u-la. A genus of marine gastropods. 

 "Criss-Cross" Inheritance. Morgan's term for that kind of 



inheritance in whicn maternal characters are transmitteu 



to sons and paternal ones to daughters. 

 Cten'-o-phore. A jelly-sphere; a member of a phyh>m of 



marine animals standing above the jelly-fishes. 

 Cy-clo'-pi-a. A monstrosity in which both eyes have fuseii 



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-ism. That form of color-blindness in which one is 



unable to distinguish 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 determines 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. 



