CYSTIC OXIDE. 



[ 185 ] 



CYSTOPTERIS. 



setigerous palp, the basal joint of which has 

 a small branchial joint with five terminal 

 digitations. First pair of jaws (fig. 21) con- 

 sisting of a large basal plate (a), with four 

 finger-like processes at its anterior extremity, 

 one of which is two-jointed, and all termi- 

 nated by several long filaments ; from the 

 outer edge of this plate arises a large elon- 

 gated branchial lamina (b), giving off from 

 its crescentic margin nineteen long pectinate 

 spines. Second pair of jaws (fig. 22) small, 

 and composed of two flattened joints, the 

 terminal one having several rigid hairs at the 

 end, and a lateral palp-like process. First 

 pair of feet (fig. 23) slender and five-jointed, 

 the last joint with a strong hook. Second 

 pair of feet (fig. 24) four-jointed, the last 

 joint terminated by two short hooks and a 

 spur-like posterior filament. Abdomen 

 (fig. 25) consisting of two long portions, 

 each with two terminal hooks, and a third at 

 its upper edge. 



C. tristriata (PI. 15. figs. 17-25). Shell 

 oval and somewhat reniform, posteriorly 

 exhibiting three narrow oblique streaks or 

 dark bands ; valves convex, green, and 

 covered with dense short hairs. Near the 

 centre of each valve are about seven small 

 clear spots. Aquatic. 



C. vidua. Shell oval, slightly sinuated 

 beneath, and with dense, short, marginal 

 hairs ; dull white ; valves marked with three 

 black, somewhat waved bands, running 

 transversely across the shell at unequal 

 distances, the most anterior being the smal- 

 lest ; posterior margin rather narrower than 

 the anterior. Aquatic. 



Twelve other British species, but none 

 very well characterized. 



BIBL. Baird, Brit. Entomostraca,ip. 161; 

 Straus, Mem. d. Mus. d. Hist. nat. vii. 1821 ; 

 Edwards, Hist. Nat. Crust, iii. 



CYSTIC OXIDE or CYSTINE. A 

 very rare component or constituent of uri- 

 nary calculi in man and the dog. It also 

 occurs in the urine, in solution and as a 

 crystalline deposit. 



Cystine is insoluble in water and alcohol ; 

 soluble in mineral acids, but not in acetic 

 acid ; also soluble in solutions of fixed 

 alkalies, their carbonates, and in solution of 

 ammonia. It is precipitated from its solu- 

 tion by acetic acid. 



Its crystals form colourless, regular six- 

 sided plates or prisms (PI. 9. group 5) ; the 

 larger crystals usually exhibit a number of 

 smaller hexagonal tables irregularly arranged 

 upon them; sometimes rectangular plates 



are met with. The crystals usually exhibit 

 but little colour with polarized light. Cystine 

 is most readily obtained in crystals from a 

 calculus, by solution in ammonia and spon- 

 taneous evaporation. 



Some of the forms of lithic acid prepared 

 artificially, resemble those of cystine (PL 8. 

 group 8 6) ; they may be distinguished by 

 the addition of ammonia, which dissolves the 

 cystine, but has little or no action upon the 

 uric acid. 



Carbonate of potash also somewhat resem- 

 bles cystine in the form of its crystals (PL 6. 

 fig. 13) ; but water or acetic acid will at once 

 distinguish them. 



BIBL. See the BIBL. of CHEMISTRY, 

 Animal. 



CYSTICERCUS, Rud. A supposed 

 genus of Entozoa, of the order Sterelmintha, 

 and family Cystica. 



Char. Individuals existing singly in a cyst, 

 and composed of a short body of a Ttenia 

 with a double crown of hooks, and termi- 

 nated posteriorly by a larger or smaller 

 vesicle. 



Head with four suctorial disks. Dujardin 

 admits five species. 



Recent researches have shown that the 

 species of Cysticercus are larval T^ENI^E. 



C. celluloses (PL 16. fig. 3). Head almost 

 tetragonal ; neck very short ; body cylin- 

 drical, longer than the vesicle; breadth of 

 cyst half an inch; length of body 1-6 to 2-5" 

 (or 1" when extended). Occurs in the 

 anterior chamber and upon the conjunctiva of 

 the eye, also in the voluntary muscles and 

 brain of man ; in the cellular tissue of the 

 pig, producing the peculiar appearance of 

 " measly pork ; " also in the ape, the dog, 

 the ox, the rat, &c. 



C.fasciolaris (PL 16. fig. 3 b, head of). 



Occurs in the liver of the rat, the mouse, &c. 



BIBL. Dujardin, Hist. d. Helminth, p. 632; 



Beneden, Cosmos, iv. and Les Vers Cestoides, 



&c., 1850. 



CYSTINE. See CYSTIC OXIDE. 

 CYSTOCOCCUS,Nag.=PROTococcus. 

 CYSTOPTERIDEJS. A subtribe of 

 Polypoda3ous Ferns, with indusiate son. 



I. Cystopteris. Sori globose. Indusium 

 subacuminate, fixed by a sublateral basilar 

 point. Veins scarcely anastomosing. 



II. Onoclea. Sori globose, one on the 

 middle of each primary vein. Indusium thin, 

 hood-like, lateral, fixed by its lower side, free 

 on the upper. Margins of the fertile leaves 

 rolled up in the form of berries. 



CYSTOPTERIS, Bernhardi. A genus of 



