GLOSSARY 



Abiogenesis. The spontaneous generation of living things from nonliving 

 matter, a theory held but not experimentally demonstrated. 



Aboral. A pole of the body opposite the mouth. 



Absorption. The passage of a fluid into living cells by osmotic or capillary 

 action. 



Achromatic. Uncolored. Free of color. 



Adaptive. Having the quality of fitness; favorable to life processes. 



Adoral. A point of the body near the mouth. 



Agamic. Without gametes. Asexual. 



Albinism. The absence of pigment in the skin, hair, feathers, eyes, etc. 



Albumin. One of the blood proteins; found also in milk, muscle, and other 

 animal substances. 



Albuminoid. A substance having many characteristics of true proteins. 



Alimentary canal. Same as digestive tract. 



Allelomorph. One of a pair of alternative characters in Mendelian inherit- 

 ance; said also of the genes which represent these characters in the 

 chromosomes. 



Amino acid. An organic acid in which one or more of the nonacid hydro- 

 gen atoms is replaced by the NH 2 group. Glycine (CH 2 NH 2 COOH); 

 Lysine (CH 2 NH 2 CH 2 CH 2 CH 2 CHNH 2 COOH). 



Amitosis. Direct cell division, in which the formation of a spindle and 

 chromosomes is lacking. 



Amoeboid. Having a flowing movement, such as occurs in Amoeba. 



Amphigony. Reproduction from a fertilized egg. Sexual reproduction. 



Anabolism. The constructive or reintegrative phase of metabolism. 



Analogous. Similar in function. 



Anastomosis. A joining or communication between vessels. 



Anatomy. The structure of organisms as determined by dissections. 



Animal pole. The yolk-free region of the egg. 



Ankylosis. Abnormal immobility and consolidation of a joint. 



Antenna. One of a pair of jointed appendages of the head of an insect, 

 or crustacean. 



Anterior. Toward the head or front end of an animal. 



Antitoxin. A complex compound, probably protein in nature, formed in the 

 blood serum and capable of neutralizing the effect of a specific poison or 

 toxin, especially such as is produced by pathogenic bacteria. 



Anus. The terminal opening of the digestive tract. 



Apical. Pertaining to or located at the apex. 



Archenteron. The cavity of the gastrula; gastrocoel. 



Arterial blood. Oxygenated blood. It may be carried by either arteries 

 or veins. 



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