DAM 



DAT 



celain shells ; a family of carnivorous 

 Gasteropods, named from the typical ge- 

 nus cyprcea ; the shells are without any 

 spire, the last whorl enveloping all the 

 others, as in the bullas. 



CYPRI'NID^ {cyprinus, the carp). 

 The Carp tribe; a family of Malaco- 

 pterygious or soft-spined fresh-water 

 fishes, having the ventral fins placed be- 

 neath the abdomen. 



C Y'PS EL A {Kvyl/fiXrj, any hollow vessel). 

 In Botany, the compound fruit of the 

 Compositae. It is one-celled, one-seeded, 

 indehiscent, with the integuments of the 

 seed not cohering with the endocarp ; in 

 the ovarial state evincing its compound 

 nature by the presence of two or more 

 stigmata ; but nevertheless unilocular, 

 and having but one ovulum. 



CYTSELINiE {cypselus, a swift). 

 Cypseline Birds, or Swifts ; a group of 

 Macgillivray's Volitatrices or Gliders, 

 remarkable for the extreme rapidity of 

 their fiight and unwearied activity. 



CYSTIBRA'NCHIANS (/cuo-rtf, a blad- 

 der, /Spdfxici} gills). A family of Isopo- 



dous Crustaceans, comprising those 

 which have the branchiae lodged in vesi- 

 cular cavities. 



CY'STICA {KvoTii, a bladder). Cyst- 

 worms or hydatids ; an order of Entozoa, 

 which have one or more buccal orifices 

 leading into a terminal cyst. 



CYSTI'DIUM (dim. of Kvan^, a blad- 

 der). In Botany, a term employed by 

 Link as synonymous with utricle. By 

 the term cystidia are denoted the pro- 

 jecting cells, or supposed male organs of 

 agarics, &c. 



CY'STULA or CISTELLA. A round 

 closed apothecium in lichens, filled with 

 sporules adhering to filaments arranged 

 round a common centre, as in sphaero- 

 phoron. The term is also applied to the 

 little open cups on the upper surface of 

 the fronds in marchantia. 



CYTOBLAST {kuto^, a cavity, /3\a- 

 (TTavw, to sprout). A nucleus observed in 

 the centre of some of the bladders of the 

 cellular tissue of plants, and regarded 

 by Schleiden as a universal elementary 

 organ. 



D 



DACTYLO'LOGY (5dKTi;Xof, a finger, 

 XoYof, an account). The art of spelling 

 words by placing the fingers in such 

 positions as to signify the letters of the 

 alphabet. Dactylology is to alphabetic 

 writing what this is to speech. 



DAGUERRE'OTYPE. A process by 

 which all images produced by the camera 

 obscura are retained and fixed in a few 

 minutes upon surfaces of silver, by the 

 action of light. The name is derived 

 from Daguerre, the inventor. 



D'ALEMBERT'S PRINCIPLE. A 

 principle in Mechanics, which may be 

 thus stated: — "If several non-elastic 

 bodies have a tendency to motion, with 

 velocities, and in directions which they 

 are constrained to change, in consequence 

 of their reciprocal action on each other, 

 then these motions may be considered as 

 composed of two others ; one, which the 

 bodies actually take ; and the other such, 

 that, had the bodies been acted on by 

 such alone, they would have remained in 

 equilibrium." 



DAMPS. The permanently elastic 

 fluids which are extricated in mines. 

 These are choke damp, or carbonic acid ; 

 100 



and fire damp, consisting almost solely 

 of light carburetted hydrogen, exploding 

 on contact with a light. 



DAOU'RITE. Rubellite. A variety 

 of red schorl found in Siberia, mixed 

 with white quartz. 



DASY'METER {haaw, dense, jueTpov, 

 a measure). A measurer of density; an 

 instrument employed for testing the 

 density of the air. It is used for this 

 purpose instead of a barometer, and is 

 sometimes called a manometer. 



DA'TA. Things given. A term used 

 in Geometry to denote certain things 

 or quantities, which are either actually 

 exhibited, or can be found out; that is, 

 which are either known by hypothesis, or 

 can be demonstrated to be known. 



DA'THOLITE. A mineral found in 

 Norway, containing boracic acid, silica, 

 and lime. See Botryolite. 



DA'TIVE CASE (dativus, from do, io 

 give). The giving case of nouns, known 

 by the signs to and for, and serving to 

 denote the remoter object to which the 

 action of the subject is directed; for 

 which, to the benefit or loss of which, 

 something is done. 



