398 BIOLOGY 



ductless glands. Gland-like structures without ducts, pouring their secre- 

 tions into the blood. 



ducts. The large spiral or otherwise marked cells in the fibrovascular 

 bundles; vessels, 106. In animals the tubes that carry the secretions 

 of glands to the exterior, 105. 



duodenum. The first loop of the intestine below the stomach, 186. 



dura mater (Lat. durus = hard + mater = mother). A tough membrane 

 on the outside of the brain, 194. 



ears, 197. 



earthworm, 155; physiology of, 216. 



ecdysis. The shedding of the skin. 



ecology (Gr. oikos = house + logos = discourse). The study of the mu- 

 tual relations of animals to each other and to their environment, 

 20. 



ectoderm (Gr. ectos = outside + derma = skin). The outer layer of cells 

 of animals, 141, 283. 



ectoparasites. Parasites living on the outer surface of their host, 230. 



ectoplasm. The outer layer of protoplasm in Protozoa, 54, 61. 



efferent nerve fibers (Lat. ex = from -}-ferre = to bear). Fibers carrying 

 impulses away from the brain, 172, 212. 



egg. Same as ovum, 267. 



egg sac, 163. 



electropism (Gr. electron = amber + trope = a turning). The power of re- 

 acting to electricity, 58. 



elements. The ultimate varieties into which substances can be chemically 

 analyzed, 5. 



embiyo (Gr. embryon = an embryo). The young organism in the early 

 stages of development, 19. 



embryology. The study of the development of the egg into an adult, 19; 

 of the frog, 280. 



embryo sac. A name formerly given to the macrospore of a flowering 

 plant, 122, 273. 



emulsion. Finely divided droplets of one liquid (usually oil) floating in 

 another liquid, 23. 



enamel. The hard, outer covering of the teeth. 



encyst. To inclose in a cyst, 74, 241. 



endoderm (Gr. endon = within + derma = skin). The inner layer of cells 

 of animals, lining the digestive tract, 143, 145, 283. 



endodermis. A layer of cells within the cortex and next to the wood in 

 the roots of plants, 113. 



endogenous stem (Gr. endon = within + genes = a producing). Stems 

 in which the fibrovascular bundles are irregularly arranged, with no 

 cambium, wood ring, or bark, 112. 



