366 GLOSSARY 



heredity, each single chromosome being termed, on this 

 account, a "Hnkage-group" by geneticists. 



Cilidte: A protozoan whose motor-apparatus consists of 

 cilia, i.e., hairlike protoplasmic projections capable of rapid 

 and coordinated vibratile movement. 



Cloaca: A common passageway through which the intestine, 

 kidneys, and sex organs discharge their products, — it 

 occurs in certain fishes, in amphibia, reptiles, and birds, 

 and in a few mammals. 



Coccyx: Lower extremity of the vertebral column in man. 



Colloids: Insoluble gumlike substances, which will not dif- 

 fuse through organic membranes. 



Commensalism: The harmonious cohabitation of two or- 

 ganisms belonging to different species', where the relation 

 is not necessarily beneficial nor necessarily harmful to 

 either. 



Crossover: The exchange or reciprocal transfer of whole 

 blocks of genes from one homologous chromosome to the 

 other, which sometimes occurs in synapsis, probably at 

 the strepsinema-stage. 



Crystalloids: Soluble substances, which usually form crys- 

 tals and readily diffuse through organic membranes. 



Cyst: A protective envelope formed around an organism 

 during period of rest. 



Cytode: The non-nucleated cell hypothecated by Haeckel. 



Cyptoplasm: The cell-body or extranuclear protoplasm of 

 a cell. 



Endomixis: A process of nuclear reorganization among the 

 protozoa, which does not require the cooperation of two 

 cells as in conjugation (amphimixis). 



Endo skeleton: An internal living skeleton providing sup- 

 port and protection (as well as organs of movement, in 

 the bone-levers to which the muscles are attached) — it is 

 characteristic of the vertebrates. 



Enzymes: Organic catalysts, i.e., complex chemical sub- 

 stances formed by organisms and serving to accelerate 

 chemical processes taking place in said organisms, e.g.y 



