cerebrum ( ser'e-brum ) : that part of the verte- 

 brate brain in which lie the centers for vol- 

 untary acts, sensation, and conscious mental 

 processes; in mammals the most anterior 

 part; it is particularly well developed in man. 



chemical change: a change in the nature or com- 

 position of a substance or group of sub- 

 stances, as opposed to physical change, which 

 leaves the nature or composition of the sub- 

 stance unchanged. 



chemistry (kem'is-tree) : the science that deals 

 with the composition of substances and the 

 changes in composition. 



chitin (ky'tin) : horny substance in the covering 

 of arthropods. 



chlorophyll (klor'oh-fill) : green coloring matter 

 in plants; necessary for making sugar. 



chloroplast (klor'oh-plast ) : small body of living 

 matter containing chlorophyll : found in leaf 

 and other green cells. 



cholesterol (koh-less'ter-ole) : fatty substance 

 found in the tissues of man and other ani- 

 mals which changes into vitamin D when 

 acted on by ultraviolet rays. 



chordates (core'datesi : members of the animal 

 phylum that includes the backboned animals 

 and a few kinds of simpler animals which 

 have a rodlike structure instead of a back- 

 bone. 



choroid (core'oid) coat: middle layer in the wall 

 of the vertebrate eyeball ; between the retina 

 and sclera. 



chromatin (crow'mat-in) : that substance in the 

 nucleus that readily takes stain; at certain 

 times found in the form of chromosomes. 



chromosome (crow'mo-soam) : one of several 

 rodlike or threadlike bodies of chi-omatin 

 that form during nuclear division. 



chrysalis (kris'a-lis) : hard-covered pupa of some 

 insects, especially butterflies. 



cilia (sil'ee-a) pi. of cilium: short hairlike projec- 

 tions from a cell, usually animal ; their wav- 

 ing may result in locomotion or production of 

 a current. 



class: in classification the largest subdivision of a 

 phylum or subphylum. 



classification: grouping plants and animals accord- 

 ing to their structure, origin, etc.; also the 

 whole system of groups that has been devel- 

 oped. 



cleavage (kleev'aj): repeated division or partial 

 division of the fertilized egg of an animal, re- 

 sulting in a mass of small cells. 



club mosses: members of a small subdivision of 

 pteridophytes (fern group) ; creeping plants 

 with erect stems bearing spores in conelike 

 structures. 



coccus (kok'us) ; pi. cocci (kok'sye) : spherical 

 bacteria. 



cochlea (kok'lee-a) : that part of the inner ear in 

 man and other mammals which contains the 

 endings of the auditory nerve. 



cocoon (kuh-koon') : silky covering spun by the 

 larvae of many insects which protects them 

 in the pupal (nonfeedingi stage; the silky 

 case in which certain spiders enclose their 

 eggs. 



coelenterates (see-len'ter-ates) : members of a 

 pliylum of water-living invertebrates whose 

 bodies have a single internal cavity, such as 

 jellyfish and corals. 



colchicine (kol'chi-seen ) : a drug (extracted from 

 a plant) which, when applied to plant tissues, 

 doubles or triples the number of chromo- 

 somes in the cell by interfering with normal 

 cell division. 



cold-blooded: applied to an animal whose body 

 temperature varies according to the tempera- 

 ture of its surroundings. 



colon (koh'lon) : large intestine. 



colony: group of animals or plants of the same 

 kind living together, usually descendants of 

 the same parents. 



composites: members of a family of flowering 

 plants having two kinds of flowers gathered 

 together into one head, as in asters and 

 daisies. 



compound: substance of which the molecules are 

 made up of two or more kinds of atoms 

 chemically united. 



conditioned response or conditioned reflex: learned 

 response in which there is reflex response to 

 a new stimulus. Pavlov produced it in dogs 

 by causing saliva to flow at the sound of a 

 bell. 



cone: a structure consisting of a mass of scales 

 bearing the reproductive parts of such plants 

 as pines, firs, and hemlocks. 



conifers (kon'i-furs) : cone-bearing trees and 

 shridjs, such as pines and firs. 



conjugation (kon-jew-gay'shun) : in sexual re- 

 production the uniting of two cells similar in 

 appearance. 



connective tissue: animal tissue that connects, 

 supports, or surrounds other tissues or or- 

 gans; occurring in various forms such as 

 white fibrous, yellow elastic, etc. 



conservation (kon-sir-vay'shun) : using natural re- 

 sources in such a way that they will not be- 

 come exhausted. 



contour (kon'toor) planting: planting crops on a 

 slope in rows which follow the curve of the 

 slope so that washing away of topsoil is re- 

 duced. 



contractility (kon-trak-til'i-ty I : that property of 

 protoplasm which enables it to change its 

 shape; particularly developed in muscle 

 cells. 



convolutions (kon-voh-lew'shuns) : ridges or folds 

 in the surface of the cerebrum or cerebellum 

 in the higher vertebrates. 



cornea (kor'nee-a) : transparent kyer that covers 

 the front of the vertebrate eye. 



corolla (ko-rol'a) : whole group of petals of a 



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