CIIORDARrA. 



[ 172 ] 



CHROMOPHYTON. 



fibrous, and that of the sheath fibro-mem- 

 branous. The cells are mostly angular or 

 polyhedral, and closely crowded. Their 

 size varies; in the embryo of a sheep rather 

 more than 1-2" in length, they measured 

 about 1-1800". 



The walls of the cells readily dissolve in 

 solution of potash ; but they yield neither 

 gelatine nor cliondrine on boiling. The 

 liquid Avithin the cells is not coagulated by 

 boiling, but the chorda itself becomes cloudy 

 and granidar. 



In its earlier stage of development, the 

 chorda consists simply of a longituduial 

 band of ordinary formative or embryonic 

 cells ; the sheath is subsequently formed. 

 It appears that the spinal column is not 

 developed from the chorda itself, but from 

 a blastema secreted by its component cells 

 and effused around them. 



The chorda is most readily examined in 

 the larvae of frogs (tadpoles), of Tritons,or of 

 Fishes, and may be separated by macerating 

 the dead animals for twenty-four hours in 

 w^ater. On cutting off the tail, it may then 

 be pressed out by gently scraping along its 

 course from the end of the tail, or from the 

 head towards the wound. It is a beautifully 

 delicate structure, and closely resembles in 

 appearance a piece of vegetable cellular 

 tissue. 



BiBL. Kolliker, Mihr. Anat. ii. 346; 

 Stannius, Verql. An.; Gegeubaur, Vert/. An. 

 450 ; Frey, Hist. 197. 



CHORDA'KIA, Ag.— A genus of Chor- 

 dariacea3 (Fucoid Algce), remarkable for the 

 solidity of the cellular texture of the fili- 

 form fronds. The axis and branches are 

 composed of a central mass of longitudinal 

 cells, upon which stand horizontal clavate 

 filaments, formed of a row of beaded cells, 

 constituting a distinct peripheral layer, 

 which gives a velvety texture and slimy 

 character to the surface. The so-called 

 spores attached to the liorizontal filaments 

 are oosj)oranf/es, and discharge zoospores 

 when mature ; trichosporanges have not yet 

 been observed. CJlaffellifonnis, MuW., is 

 common on rocks and stones between tide- 

 marks. 



BiBL. Harvey, Br. Mar. Ah/, pi. 10 A ; 

 P/n/c. Brit. pi. ill ; Thuret, Ann. Sc. 

 Nat. 3 ser. xiv. 237. 



CTIOHDARIA'CEyE.— A family of Fu- 

 coid Alg;e. Olive-coloured sea-weeds with 

 a gelatinous or cartilaginous, branching 

 frond, composed of vertical and horizontal 

 filaments uiterlaced together; the uospo- 



ranges and trichosporanges attached to the 

 filaments forming the supei'ficial layers of 

 the frond. British genera : 



Chordaria. Axis cartilaginous, dense fila- 

 ments of the circumferauce unbranched. 



Mesocfloia. Axis gelatinous, loose fila- 

 ments of the circiuufereuce branching, 



BiBL. Harvey, Marine Algce ; Thuret, 

 Ann. Sc. Nat. 3 ser. xvi. o, &c. See also 

 the genera. 



CHORIOP'TES, Gervais.— A subgenus 

 of Sarcoptes, with the body bilobed, or 

 notched posteriorly, the mandibles short, 

 didactylous, the tarsi with strong claws, 

 and very large suckers. 



C. bovis (spathiferns) ; on the legs and 

 hind quarters of the horse, the goat, and 

 the ox ; C. setifertis, on the hyseua and fox ; 

 C. ecaudatus, in the ears of dogs, cats, and 

 ferrets. There are other doubtful species. 



BiBL. Megnin, Parasites, liJS (figs.) ; 

 Murray, Ec. Entom. 312 (fig). 



CHORIZOP'ORA = Lepralia pt. C. 

 Brominiartii. Cells connected by a tubular 

 network. Marine. 



BiBL. Hincks, Pohjzoa, 222. 



CHOROID MEMBRANE. See Eye. 



CHROMATE OF LEAD (neutral) is ,.ne 

 of the best materials for coluuring size in 

 injections. See Lvjection. 



CHROMIC ACID may be prepared by 

 adding gradually from 120 to loO parts, by 

 volume, of pure concentrated sulphuric acid 

 to 100 parts of a; cold saturated solution of 

 bichromate of potash. The crj-stals of the 

 acid separate as the solution cools. The 

 mother-liquor should be poiu'ed off", and the 

 crystals dried upon a tile; they may be 

 ptu'ified by re-crystallization from solution 

 in water. With excess of sulphuric acid, 

 chromic acid is a valuable reagent for 

 dissolving the intercellular stibstance of 

 phints. 



Chromic acid is readily decomposed by 

 organic matter, as dust &c., and must 

 therefm-e be preserved in a well-stoppered 

 bottle. Its aqueous solution, which should 

 be of a pale yellow colour, is used for 

 hardening and preserving nervous and mus- 

 cuhir tissues, &c. It should bo prepared 

 when required. 



CIIROMOPirYTOX, Woronin. — A 

 doul)tful organism, probably allied to the 

 Palmellaceoo, forming a yellow isli-brown 

 dust on the surface of boggy pools (Finland). 

 Two forms were met with : the larger con- 

 sisted of splicrical moniliform or variable 

 bodies, composed of a hyaline matrix, con» 



