484 THE PINEAL ORGAN 



Ccelenterata (Gr. koilos, hollow ; enter on, bowel) : the phylum which com- 

 prises the polyps, sea-anemones, and jelly-fishes, in which there is an 

 enteric cavity lined by entoderm. 



Coleoptera (Gr. koleos, sheath ; pteron, wing) : an order of the Insecta — 

 beetles in which the anterior pair of wings are modified to form a hard, 

 protective covering for the posterior membranous wings. 



Compound eye : a term which is applied in two senses — (1) An eye consisting 

 of several strata of cells, e.g. (a) receptive (rod and cone cells), (b) inter- 

 mediate (bipolar cells), (c) retinal ganglionic cells ; (2) a composite or 

 aggregate eye in which the whole is composed of an aggregate of units, 

 each of which is called an ommatidium. 



Conarium (Gr. konarion, dim. of konos, cone) : the epiphysis cerebri, so named 

 on account of the conical form in man and certain mammals. 



Convergence : the acquisition of a similar form or structure by two or more 

 different organisms as a result of a similar mode of life ; as contrasted 

 with resemblances which are due to inheritance from a common 

 ancestor. 



Copiophora cornuta (Gr. kopis, a curved knife, sting ; phoreo, bear ; L. 

 cornuta, horned) : a species of locust in which there is a single, median 

 frontal ocellus of large size. 



Coregonus : a genus of fresh-water fishes belonging to the family Salmonidae ; 

 commonly known as " white fish." 



Corneagen cells (L. cornu, horn ; rt. gen, give origin to) : the epidermal 

 cells which produce the superficial non-cellular or horny layer. When 

 the cells form a single stratum of tall columnar cells, this layer is some- 

 times spoken of as the palisade layer. 



Crangon : sea-water shrimp belonging to the sub-class Malacostraca, or soft- 

 shelled crustaceans. 



Cretaceous System or Period (L. creta, chalk) : the uppermost chalky deposits 

 of the mesozoic or secondary era, in which remains of bony fish are 

 abundant. 



Cumacea : an order of the Malacostraca, including Diastylis. The eyes are 

 sessile, close together, or fused into one. They are always poorly 

 developed and occasionally are wanting. 



Cuticle (L. cuticula, the thin outer layer of the skin) : the most superficial 

 layer of an epithelial sheet, which is either secreted by the epithelial 

 cells or formed by degeneration of the most superficial cells of the 

 epidermis. It may be impregnated with lime salts or chitin. 



Cyathaspis (Gr. kuathos, cup ; aspis, shield) : an extinct Pteraspid fish belong- 

 ing to the class Ostracodermi, characterized by a bowl or cup-like head- 

 shield. 



Cyclops (Gr. cyclops, the mythical one-eyed giants described by Homer : 

 literally round-eyed) : the water-flea or Daphnia, in which the paired 

 lateral eyes have fused into a single organ. 



Cyclostomata (Gr. kuklos, circle ; stoma, mouth) : a primitive class of fishes, 

 characterized by their round mouths and absence of jaws, including the 

 lampreys and hag-fishes. 



