CONDENSER. 



[ 158 ] 



CONFERVOIDE^. 



the nature or proportion of the respective 

 constituents, they mostly exhibit a laminated 

 structure. This is visible to the naked eye 

 in the larger ones, and evidenced in those 

 which are microscopic by the appearance of 

 concentric rings, and of a nucleus or nuclei. 

 These concentric rings and nuclei are dis- 

 tinguishable equally in concretions formed 

 artificially and in those occurring naturally. 



It has been imagined that urinary concre- 

 tions and calculi owe their origin to a process 

 of cell-secretion. We beUeve this view to be 

 untenable. 



BiBL. Taylor, Hunterian Catalogue, Cal- 

 culi; Qnekett, Med. Times, 1851. xxiv.p.551; 

 Griffith, Me^/. Times and Gaz. \852. xxv. p. 272^ 

 and the Bibl. of Chemistry, Animal. 



CONDENSER, ACHROMATIC— In- 

 troduction, p. xvi. We omitted to no- 

 tice that the "new condenser" mentioned at 

 p. xvii. is called after the inventor, "Gillett's 

 Condenser." 



CONDENSER, BULL'S-EYE, &c., 

 foropake objects. Introduction, p. xviii. 



CONFERVA, Plin.— A genus of Confer- 

 vace8e(Confervoid Algae), which, as restricted 

 here, contains chiefly marine species ; but 

 we have thought it advisable to retain in it 

 the species separated by Kiitzing as Chceto- 

 morpha and Thuret as Microspora, so that 

 our Conferva corresponds to Hassall's pro- 

 posed genus Aplonema. The plants consist 

 of unbranched filaments, composed of cylin- 

 di-ical cells, the length and diameter of which 

 have a very variable relation in diff*erent spe- 

 cies. They are reproduced by zoospores 

 formed from the cell-contents. Al. Braun 

 says that C. bombycina produces four in a 

 cell. According to Thuret, C. cerea produces 

 large numbers, which escape by a lateral 

 orifice, while the species he describes as Mi- 

 crospora floccosa forms a number which 

 escape by a circular dehiscence breaking up 

 the filaments. The zoospores are 2-ciliated 

 in general, but sometimes bear four. The 

 spores have not been observed ; and hence 

 Kiitzing has suggested that C. bombycina, 

 and the other species of Conferva he ad- 

 mits, may be young states of CEdogonium, 

 but the true (Edogonia produce solitary zoo- 

 spores with a crown of cilia. British spe- 

 cies : 



Freshwater. 

 1. C. bombycina, Ag. Filaments 1-360 to 

 1-180" in diameter, four or five times as long, 

 forming a yellow-green cloudy stratum. 

 Common in stagnant water. Dillw. Con- 

 fervce, pi. 60. 



2. C. floccosa, Ag. (PI. 5. fig. 116). More 

 robust; articulations once or twice longer 

 than broad. Microspora floccosa, Thuret, 

 Ann. des Sc. nat. 3 ser. xiv. pi. 17. fig- 6, 7- 



Marine. 



Thirteen species are described by Harvey 

 {Brit. Marine Algce), of which C. «rea, Dillw. 

 is one of the commonest, remarkable for the 

 large size of the tufted filaments, as thick as 

 hog's-bristles, growing 3 to 12" long, of a 

 yellow-green colour. C Melagonium, Web. 

 and Mohr, has erect tufted filaments equally 

 thick, while C. Linum, Roth, has entangled 

 filaments twice as thick, deep glossy green, 

 and many feet long. 



The cell-walls of these large marine species 

 present a curious striated appearance when 

 treated with acids, which has led J. Agardh, 

 apparently erroneously, to suppose they are 

 composed of spu'al filaments. (See Spiral 

 Structures.) 



Bibl. Harvey, loc. cit. Phyc. Britan. ; 

 Thuret, loc. cit. ; Kiitzing, Species Alg. ; 

 Hassall, Brit. Freshw. Alg. 213 ; Al. Braun, 

 Rejuvenescence, Sfc, Ray Soc. Vol. 1853. 

 p. 184. 



CONFERVACEiE.— A family of Confer- 

 voideae. Marine or freshwater Algae ; com- 

 posed of articulated filaments, simple or 

 branched, without enveloping gelatine ; cells 

 cylindrical, shortish, not conjugating. Re- 

 production by zoospores and globular spores 

 produced from the cell-contents. 



Synopsis of the British Genera. 



1. Cladophora. Filaments tufted, much 

 branched. Sea and freshwater. Zoospores 

 minute, many in a cell. 



2. Rhizoclonium. Filaments decumbent, 

 with small root-like branches. Zoospores 

 minute, numerous. Sea, brackish, and fresh- 

 water. 



3. Conferva. Filaments unbranched. 

 Zoospores minute, numerous in the cells. 

 Sea, brackish, and freshwater. 



4. CEdogonium. Filaments simple, with 

 very thick walls and mostly short joints, 

 often swollen to produce a spore or a zoo- 

 spore, and with annular striae near the cross 

 septa. Zoospores single, large, composed of 

 the entire contents of a cell, crowned with a 

 wreath of cilia. Freshwater. 



Bibl. See the genera. 



CONFERVOIDEiE or CHLOROPO- 

 REiE.— An order of Algae. The Chloro- 

 spores or Confervoids, the lowest order of 

 the Algae, display a preponderating number 

 of truly microscopical plants, and constitute 



