GLOSSARY 505 



CHO'-RI-ON. A tough membrane around an egg secreted by 



.surrounding cells. 



CHRO'-MA-TIK. The deeply staining substance of the nucleus. 

 CHHO'-MO-SOMES. Deeply staining bodies found in the nucleus 



at the time of indirect division. 

 CII/-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 transmitted 



to sons and paternal ones to daughters. 

 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-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'-THAL 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. 



