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. 



embj-yo (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. 



