906 TEXTBOOK OF ZOOLOGY 



Asymmetry (a sim'et ri), a condition in which the two sides of an animal are 



dissimilar. 

 Autonomic nervous system (6 to nom'ik), that portion of the nervous system 



controlling the involuntary muscles. 

 Autotomy (otot'omi), self -mutilation. 

 Axial gradient (ak'si al gra' di ent), the graduation of the rate of metabolism 



along the principal axis of an axiate animal. 

 Axone (ak'son), a nerve fiber serving to conduct impulses away from a nerve 



cell body. 



Barrier (bar'ier), any physical, chemical, or biological obstruction that pre- 

 vents migration of animals. 



Benthos (ben'thos), life of the deep sea bottom. 



Binary fission (bi'nari fish'iin), division of a cell into two daughter cells. 



Biramous (bira'miis), a two-branched condition. 



Bisexual (bi sek'sh 6b al), a condition in which both male and female organs 

 are present in one individual. 



Bivium (biv'ium), one side of an echinoderm including a pair of ambulacra. 



Blastocoele (blas'to sel), the cavity present in the blastula stage of develop- 

 ment; also cleavage of segmentation cavity. 



Blastomere (blas'to mer), one of the segments first formed by the division of 

 the ovum. 



Blastula (blas'tula), a sphere of cells with a hollow cavity resulting from 

 cleavage of the zygote. 



Blepharoplast (blef'a ro plast), the bodj^ in a cell from which a flagellum 

 arises. 



Brachium (bra'kium), arm. 



Branchial (brang' ki al), pertaining to gills or branchiae. 



Buccal (buk'al), pertaining to the mouth cavity. 



Budding (bud'ing), reproduction involving the branching of new individuals 

 from the external surface of the old one. 



Byssus (bis'iis), a tuft of fiberlike threads which attach certain mussels to the 

 substratum. 



Caecum (se'kum), a blind pouchlike pocket of the intestine; usually at the 



junction of the small and large intestines. 

 Calcareous (kal kar'e us), composed of lime or calcium salts. 

 Calciferous (krd sif'er us), glands which are thought to secrete an alkaline 



secretion into the esophagus of the earthworm. 

 Canaliculus (kan'alik' u lus), one of the tiny canals extending from lacuna 



to lacuna to distribute nutriment in bone. 

 Capillary (kap'ileri), a microscopic branch of an artery which extends into 



a tissue and finally joins a small vein. 

 Carapace (kar'apas), shell-like external covering. 

 Carbohydrate (kar bo hi'drat), organic compound of carbon, hydrogen, and 



oxygen, such as starch or sugar. 

 Cardiac (kar'diak), pertaining to the heart. 

 Carnivorous (kjir niv'6 rus), flesh eating. 

 Caste (kast), any group of distinct forms within a species, as found in some 



insects. 

 Cataholism (ka tab' 6 lizm), process of oxidation or break-down of protoplasm; 



destructive phase of metabolism; dissimilation; the oxidation of organic 



substances of the body to release kinetic energy and heat. 

 Catalysis (ka tal'i sis), the initiation or acceleration of a chemical reaction 



by the presence of a substance which itself does not enter into the 



reaction, as an enzyme. 

 Caudal (ko'dol), pertaining to the tail. 



