396 BIOLOGY 



crystalline. Applied to substances that will dialyze through membranes, 

 307 



crystalline lens. The lens in the eyeball which focuses light on the retina. 

 197. 



Culex, 72. 



cutaneous (Lat. cutis = skin). Pertaining to the skin, 191, 209. 



cuticle (Lat. cutis = skin). A thin, structureless membrane forming on 

 the outside of the epidermis, 62, 166. 



cyclical changes. Changes which pass through a cycle but eventually 

 return to the starting point, 5. 



cyst. A hard shell which is sometimes secreted around organisms in a dor- 

 mant condition; any sac with a wall, developing abnormally in the 

 body, 59, 74, 241. 



cytoblastema, 38. 



cytoplasm (Gr. cytos = cell -f plasma = substance). The liquid part of 

 the protoplasm outside the nucleus, 32, 49. 



dandelion, 370. 



DARWIN, 352. 



death, 3, 153. 



decay. Decomposition changes produced by bacteria in the presence of 

 air; more complete than putrefaction, 81. 



deciduous. A term applied to plants that shed their leaves in the fall; 

 also to mammals that shed the placenta at birth. 



decomposition. The chemical destruction of molecules. In biology the 

 disintegration of organic substances, usually produced by bacteria or 

 allied organisms. 



degeneration, 233. 



dehiscence (Lat. dehiscere = to open). The opening of an organ to dis- 

 charge its contents, 123. 



dendrites (Gr. dendron = tree) . The branching processes arising from 

 neurons, 170. 



denitrification. The reduction of nitrates to nitrites or simpler compounds. 



dentine. The inner, softer part of the teeth. 



depressant. Having the power of reducing activity. 



dermis. The inner layer of the skin, 176. 



descent theory. The theory that all organisms are genetically inter- 

 connected: evolution, 348. 



dessication (Lat. dessicare = to dry up). Drying, 57. 



destructive processes, 139, 300. 



deutoplasm (Gr. deuteros = second + plasma = substance). The food 

 yolk in the egg, 249. 



DE VRIES, 357. 



