GENERAL ZOOLOGY 



condition the appearance of black hair, and an allelomorph, gene a, might con- 

 dition the appearance of white hair. 



ALTERNATION OF GENERATIONS. See METAGENESIS. 



ALVEOLUS {pi ALVEOLI). A small cavity, such as any one of the minute air sacs in 

 the mammalian lung or a secreting portion of an alveolar gland. 



AMBULACRAL. Pertaining to the rows of openings through which the tube feet of 

 echinoderms are extended; hence, ambulacra! system of which the tube feet are 

 a part. 



AMINO ACIDS. Organic acids containing one or more amino groups (-NH.,); units 

 of which proteins are composed. 



AMITOSIS. Direct nuclear division, without the formation of chromosomes. Cf. 

 MITOSIS. 



AMOEBOID. Pertaining to or resembling an amoeba; usually used with respect to 

 locomotion. 



AMPHIBIOUS. Living both on land and in water. 



AMPHIMIXIS. The fusion of the nuclei of the two gametes that give rise to a zygote. 



AMPULLA {pi. AMPULLAE). A flask-shaped structure. 



ANABOLISM. Collective term for synthetic reactions of cellular metabolism. Cf. 

 CATABOLISM. 



ANAEROBIC. Able to live in the absence of free oxygen. 



ANALOGY {adj. ANALOGOUS). Correspondence in function. Cf. HOMOLOGY. 



ANATOMY. The science of the structure of animals as revealed by dissection; gross 

 morphology. Cf. HISTOLOGY. 



ANIMAL HEMISPHERE. That half of a telolecithal egg in which the nucleus is located 

 and which contains less yolk than the vegetal hemisphere. 



ANIMAL POLE. That point on the surface of an egg at which the polar bodies are 

 formed; one end of the egg axis. Cf. VEGETAL POLE. 



ANISOGAMETES. Gametes of unequal size that unite in pairs. Cf. ISOGAMETES. 



ANISOGAMY. Fusion of gametes of unequal size. Cf. ISOGAMY and FERTILIZATION. 



ANTERIOR. Pertaining to or situated toward the head; the end which is directed for- 

 ward during locomotion; the end which contains the mouth. Cf. POSTERIOR. 



ANTHROPOLOGIST. One who studies the science of mankind. 



ANUS. The posterior opening of the digestive tract. 



APPENDAGE. Any limb or peripheral part of the body that diverges from the prin- 

 cipal axis; specifically, the limbs of arthropods and vertebrates. 



AQUATIC. Pertaining to water; living in water. 



ARCHENTERON. The gastrula cavity. 



ARREST. Suspension of a movement or process. 



ARTERY. A blood vessel carrying blood from the heart to capillaries. Cf. VEIN. 



ARTHRO-. Combining form, meaning "joint." 



ARTIFACT. A natural object modified by man, such as a stone implement. 



ARTIFICIAL PARTHENOGENESIS. See PARTHENOGENESIS. 



ASEXUAL. Not sexual or not produced by sexual processes. 



ASEXUAL REPRODUCTION. Reproduction without formation and union of gametes. 

 Cf. SEXUAL REPRODUCTION. 



ASSIMILATION. I'he taking up by the cells of useful substances brought to them bv 

 the circulating fluids, and the utilization of these substances in metabolism. Cf. 

 ANABOLISM. 



ASYMMETRY. Absence of symmetry. 



ASYMPTOTE. A line that approaches nearer to some curve than any assignable dis- 

 tance, but, though infinitely extended, would never meet it. Characteristic of 

 the logistic curve describing the growth of populations of organisms. 



ATRIUM {pi. atria). A membranous sac which serves as a passageway, such as the 

 atrium (auricle) of the heart and the genital atrium. 



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