120 THE SMALLEST LIVING THINGS 



Chlorophyll: the green coloring matter in plants. 

 Chloroplastid: a plastid forming and containing chlorophyll. 



Chromatin: a protoplasmic substance found in the nucleus of cells; regarded by 

 many as the physical basis of heredity : It exists in small granules, which at 

 cell division become aggregated into chromosomes. 

 Chromatoid granules : granules like those which contain chromatin. 

 C H rom atop h ores : the color bodies found commonly in plant cells ; they include 

 both green chloroplastids and red or yellow chromoplastids, and vary greatly in 

 form and size. In certain lower forms of algae they afford sustenance to the 

 organism. 

 Chromosome: one of the small bodies into which the chromatin of a cell nucleus 



resolves itself previous to cellular or nuclear division. 

 Cilia (singular, cilium) : hairlike processes, found on many cells, capable of a 

 vibratory or lashing movement. Unlike pseudopodia (q.v.) cilia are permanent 

 processes, and in many cases keep in incessant motion. In free-swimming uni- 

 cellular organisms, and some small multicellular forms, cilia serve as organs 

 of locomotion. In the higher animals their usual function is to produce a 

 current of fluid. For example, in man ciliated cells line the nasal cavity, the 

 trachea, the bronchi, etc., and by a constant propulsion toward the nose assist 

 the removal of mucus and dust particles. 

 Ciliates : a sub-phylum of protozoa having cilia in the immature stages (Suctoria) 



or throughout life (Cilia fa). 

 Cirrus (plural, cirri) : in protozoology coalesced cilia forming complex motile 



organs which are circular in cross section. 

 Coccoid bodies : reproductive bodies occurring in spirochaetes ; equivalent to bac- 

 teria spores. 

 Columella : in zoology and anatomy, any of various parts which can be likened 



to a column (cf. newel post in a winding staircase). 

 Conjugation: the temporary fusion of two unicellular organisms, involving a 

 union of their nuclei or an interchange of nuclear material. Though male and 

 female cells are not distinguished, the process is analogous to fertilization 

 among higher organisms. 

 Cortex : the outer or superficial part of an organ, especially the outer layer of 

 gray matter of the brain; also the outer part (ectoplasm) of certain organisms, 

 as some of the protozoa, the internal portion being called the endoplasm. 

 Cortical zone : the outer layer of living protoplasm ; see Cortex. 

 Cytology : the branch of biology which treats of cells. 

 Cytoplasm : the protoplasm of the cell exclusi\e of the nucleus. 

 Decompose: to resolve into original elements or into simpler compounds. 

 Derived organization : the final stage of development of an organism. 

 Desmid (from the Greek word meaning "chain") : an unicellular alga. 

 Diatom (from the Greek, meaning "cut in two") : any unicellular alga belonging 

 to the order Bacillariales ; diatoms are remarkable for a silicified cell-wall which 

 persists as a skeleton after the death of the organism and forms kieselguhr. 

 Diatoms are always found on submerged objects (wood, stones, etc.) to which 

 they may impart a slimy feeling. Kieselguhr is a fine, usually white powder, and 

 is used as an absorbent in dynamite and as a polishing material. 

 Dorsal: pertaining to, or situated near or on, the back (dorsum) of an animal 



or of one of its parts — opposed to ventral. 

 Electrolyte: a compound substance which can be decomposed (separated) into 

 its elements by an electric current. Salts, as a rule, disassociate readily, acids 

 in various degrees. Substances which do not conduct an electric current are 

 called nonelectrolytes. 

 Encystment: the process of forming a cyst or of becoming enclosed in a capsule; 



the state of being encysted. 

 Endomixis (adjective, endomictic ; from the Greek endo, meaning "within" and 

 mixis, a mixing) : dissolution of the macronucleus (q.v.) of an infusorian and 

 its reorganization from micronucleus (q.v.) without the intervention of con- 

 jugation (q.v.). 

 Endosmosis : see Osmosis. 



Enzyme: any of a number of complete organic substances capable of effecting 

 catalysis (q.v.) ; enzymes are sometimes called unorganized, unformed, or 



