GENERAL ZOOLOGY 



CONDITION, lo be a prerequisite of some event. 



CONDITIONED REFLEX. A reflex action in wliich the reaction to a stimulus has been 



established by training; or experimentation. 

 CONJUGATION. Temporary union of two cells during which exchange of nuclear 



materials occurs, as in Paramecium. Cf. FERTILIZATION. 

 CONNECTIVE. A longitudinal nerve cord extending between ganglia in difTerent 



regions of the body. Cf. COMMISSURE. 

 CONSTITUENT. That which is a necessary part. 

 COORDINATION. The working together of difTerent parts of an organism in such a 



way that it is physiologically balanced. Cf. CHEMICAL COORDINATION and 



NERVOUS COORDINATION. 

 COPULATION. See SEXUAL UNION. 



CORTEX ipl. CORTICES). An outer or superficial layer. 

 CRANIAL. Pertaining to the sicull. 

 CROSS-FERTILIZATION. Union of gametes produced by different individuals. Cf. 



SELF-FERTILIZATION. 

 CUTICLE. A non-cellular organic layer secreted by the cells of the outer surface of the 



body. 

 CYST. .A. protective capsule. 

 CYTOLOGY. The science of the structure of cells. 

 CYTOPLASM. 1 he contents of the cytosome. 

 CYTOPLASMIC INCLUSIONS. Microscopic structures found in the cytoplasm, such as 



mitochondria and volk spheres. 

 CYTOPYGE. Cell "anus" through which fecal material is egested by some protozoans. 

 CYTOSOME. The part of the cell surrounding the nucleus and limited by the cell 



membrane. 

 CYTOSTOME. Cell "mouth" through which food is ingested by some protozoans. 



DATA {sing. DATUM). Observed and recorded facts. 



DERMAL. Pertaining to the skin or outer covering of the body. 



DERMIS. The inner layer of the skin, composed of connective tissue. 



DETERMINERS. See GENES. 



DEVELOPMENT. The transformation of a zygote into a multicellular organism; the 



consecutive processes of cell division, cell localization, and cell differentiation 



following syngamv. 

 DI-. Combining form, meaning "two"; same as BI-. 

 DIAPHRAGM. A partition; specifically, the partition forming the anterior boundary 



of the peritoneal cavity in mammals. 

 DIFFERENTIATION. See CELL DIFFERENTIATION. 

 DIFFUSE. To spread, as a fluid; to mix with another substance. 

 DIGAMETIC SEX. The sex of individuals that produce two classes of gametes which 



differ with respect to the presence of an X-chromosome; in most animals, the 



male sex. 

 DIGESTION. The chemical disintegration of food which precedes its absorption and 



utilization. 

 DIGESTIVE. Pertaining to digestion. 

 DIOECIOUS. Having sexually differentiated individuals; having the male and female 



gonads in separate individuals. Cf. MONOECIOUS. 

 DIPLOBLASTIC. Having only two germ layers, the ectoderm and endoderm, and a 



single cavity which has one external opening and is lined with endoderm. Cf. 



MONOBLASTIC and TRIPLOBLASTIC. 

 DIPLOID. Having two sets of chromosomes forming homologous pairs, as in somatic 



cells, primordial germ cells, and zygotes. Cf. HAPLOID. 

 DIRECT CELL DIVISION. See AMITOSiS. 



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