GONIOTIIECIUM. 



[ 295 ] 



GORGONIA. 



GONIOTHECIUM, Ehr.— A genus of 

 fossil Diatomacere. 



Char. Frustules geminate, terete, witli a 

 median (longitudinal) constriction (suddenly 

 attenuate and truncate at the ends, hence 

 appearing angular). Corresponding to Pyxi- 

 dicula, constricted in the middle, and trun- 

 cate at the ends. 



Found in America. 



The characters of the nine or ten species, 

 as well as in fact those of the genus, have 

 been very imperfectly described. 



BiBL. Ehrenberg, Abhandl. d. Berl. Akad. 

 1841. p. 401, and Ber. d. Berl. Akad. 1844. 

 p. 82; Kiitzing, Bacill. p. 51, and Sp. Alg. 

 p. 23. 



GONIUM, Miiller.— A genus of Volvo- 

 cineae (Confervoid Algae) forming microsco- 

 pic, square, flat fronds, either ciliated and 

 endowed with a power of motion, or devoid 

 of cilia and motionless; it is possible that 

 these two conditions are only stages of deve- 

 lopment in species active at one time and 

 resting at another. The perfect fronds are 

 composed of usually sixteen cells enclosed 

 in wide, colourless coats (young fronds but 

 four cells, some kinds have more than six- 

 teen), united together into flat, square masses 

 by adherence at various points of their cir- 

 cumference; a light vacuole in the sub- 

 stance of the cell-contents may often be ob- 

 served to exhibit a rhythmical contraction and 

 expansion, as mVolvox', the cells of the active 

 forms having each a pair of vibratile cilia, 

 which run out from the central protoplasmic 

 mass, through the hyaline envelope, and 

 project as free processes, rowing the frond 

 about in the water. They are commonly 

 observed to increase by division, a frond 

 composed of sixteen cells breaking up into 

 four fronds, each composed of four cells, &c.; 

 but it is probable that other kinds of deve - 

 lopment exist, and that the motionless forms 

 are resting states of active species. Gonium 

 pectorale is an exceedingly interesting micro- 

 sco])ic object, not uncommon in freshwater 

 pools. Ehrenberg, who regards them as 

 Infusoria, describes the following species. 



1. G. pectorale (PI. 3. fig. 11). Frond 

 square, composed of sixteen bright green 

 cell-masses, enclosed in hyaline envelopes, 

 each with a pair of cilia ; size of green masses 

 1-1960 to 1-1150"; frond not exceeding 

 1-280". In clear water, salt and fresh, near 

 the surface. 



2. G. punctatum. Cells sixteen ; cell- 

 masses green, with black granules; diam. 

 1-4600"; frond of sixteen, 1-576". 



3. G. tranquillum (PI. 3. fig. 12). Cells 

 sixteen; cell-masses green, diam. 1-2880"; 

 frond of sixteen, 1-144 to 1-288", sometimes 

 twice as broad as long; the cell-masses 

 found in division (binate or quaternate), 

 motionless. (Possibly not a Gonium, but a 

 Palmellacean) {Tetraspora'?). 



4. G. hyalinum. Cell-masses hyaline, 

 diam. 1-3000"; frond of twenty or twenty- 

 five, 1-600". In stagnant water. 



5. G. glaucum. Cell-masses bluish-green, 

 from four to sixty-four in a frond, diam. 

 1-7000 to 1-4200", ditto of frond not ex- 

 ceeding 1-570". In sea-water. 



The remarkable organism Sarcina re- 

 sembles the motionless Gonia in structure, 

 but its peculiar habit would rather lead to 

 its being placed among the Fungi. The 

 genus Tetraspora among the Palmellaceae 

 is closely related here. Merismop^dia 

 seems to be an unnecessarj^ genus, as the 

 species may fall under one or other of these. 



BiBL. Ehrenberg, Infusionsth. p. 55; 

 Cohn, Nova Acta, xxiii. p. 169. pi. 18. 



GORDIUS, Linn, — A genus of Entozoa. 



Char. Body very long and slender, fili- 

 form; alimentary canal with a single orifice; 

 sexes distinct. 



G. aquaticus, the common hair-worm, is 

 from 7 to 10" in length and about 1-25 to 

 1-20" in breadth, of a brown or blackish co- 

 lour, and is found in water or damp places. 

 The mouth is very indistinct ; the tail of the 

 male is bifid, that of the female simple and 

 rounded. 



The ova, agglutinated in long strings, are 

 deposited in water, and being devoured by 

 insects, undergo development within their 

 bodies. 



These animals frequently coil themselves 

 into a knot-like form, whence the name. 



See Mermis. 



BiBL. Dujardin, Hist. nat. d. Helminth. 

 p. 296, and Ann. des Sc. nat. 1842. xviii. 

 p. 142; Siebold, Lehrh. d. Veryh Anat., 

 Entomol. Zeitung, 1842-43, and Erich son's 

 Archiv, 1843. ii. p. 302; Berthold, Ueberden 

 Bau d. Wasserkulbes, 1842. 



GORGONIA, Linn.— A genus of Polypi, 

 of the order Anthozoa. 



Char. Polypidom attached by a kind of 

 root, consisting of a central, branched, horny 

 and sometimes anastomosing flexible axis, 

 coated with asoft andfleshy polypiferous crust. 



The species, of which there are four Bri- 

 tish, are popvilarly known as sea-fans ; they 

 are not microscopic, often attaining very 

 considerable dimensions. 



