GRANULE-CELLS. 



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GREGARINA. 



Spicula simple, radiate or stellate, com- 

 posed of carbonate of lime ; hence easily 

 distinguished from the siliceous spicula of 

 other sponges by their dissolving with effer- 

 vescence in a dilute acid. The organic basis 

 is stated not to be fibrous as in most other 

 sponges. 



The British species are found growing 

 upon or from rocks, sea-weeds, shell-fish 

 and zoophytes, between tide-marks. They 

 vary in size from about the 1-10 to 3 or 4". 

 Gemmules have not been found. 



BIBL. Johnston, Br. Sponges, 172; Grant, 

 Compar. Anat. and New Phil. Jburn. i. and 

 ii. ; Bowerbank, Br. Spong. ii. 1. 



GRANULE-CELLS. This term has 

 been applied to cells fonnd in animal solids 

 and liquids containing a number of globules 

 of fat or oil (PL 38. figs. 7, 16 a, 17 e). They 

 are of variable size, perhaps the average 

 may be placed at 1-2000" ; and are easily 

 recognized by the dark margins and light 

 centres of the globules, which are insoluble 

 in acetic acid and solution of potash. The 

 cells sometimes contain a nucleus, at others 

 not. The term granule-cells should pro- 

 perly be limited to cells of new formation, 

 as those found in inflammation, cancer, &c. ; 

 but it has been so generally applied to cells 

 of whatever kind, containing fatty globules, 

 that it has no pathological signification. 



See DEGENERATION, FATTY, and INFLAM- 

 MATION. 



GRANULOSE. See STARCH. 



GRAPE-FUNGUS. See OIDIUM. 



G RAPHID 'El. A tribe of Lichenaceous 

 Lichens, having a thin, crustaceous, scarcely 

 visible or subepidermal thallus, with lirel- 

 line apothecia. 



It includes the British genera : Agyrium, 

 Arthonia, Chiodecton, Glyphis, Graphis, 

 Lithoyrapha, Melaspilea, Opegrapha, Platy- 

 grapha, Ptychographa, Stigmatidium, and 

 Xylographa. 



BIBL. Leighton, Brit. Lichen-Flora, 390. 



GRA'PHIS, Ach. A genus of Graphi- 

 dei, containing ten British species, very va- 

 riable in their appearance ; mostly whitish 

 or yellow papery expansions on the bark of 

 trees, beset with irregular black markings 

 (lirelline apothecia) like writing. 



BIBL. Leighton, Brit. Lich.-Fl 426. 



GRASSES. A family of Monocotyledo- 

 nous Flowering Plants, remarkable in many 

 respects for their microscopic structure, 

 especially the siliceous EPIDERMIS and the 

 STARCH grains in the ALBUMEN, for which 

 see those heads. 



GRATELOU'PIA, Ag. A genus of 

 Cryptonemiaceas (Florideous Algae), repre- 

 sented by a very rare British species, G.fli- 

 cina, seldom growing more than 2 inches 

 high with us. Fructification minute, im- 

 mersed, favellidia opening by a pore, and 

 cruciate, tetraspores vertically placed among 

 the filaments of the periphery. 



BIBL. Harv. Mar. Alg. 137, pi. 17 A; 

 Grev. Alg. Brit. pi. 16. 



GREENSAND. According to the ob- 

 servations of Ehrenberg and Bailey, the 

 glauconitic grains frequent in many geolo- 

 gical deposits, especially in certain beds 

 known as Greensaud, are formed of foasilizod 

 organic bodies, mostly casts of Foramini- 

 fera. 



BIBL. Ehrenberg, Abh. Berl Akad. 1856, 

 85-176; Monatsber. 1858, 328; Bailey, Ann. 

 N. H. s. 2. xviii. 425; Parker & Jones, Ann. 

 N. H. s. 4. x. 263 ; Sollas, Geol. Mag. 1876, 

 539. 



GREGARFNA, Dufour. This curious 

 group of organisms, which was formerly 

 placed among the Entozoa, is now placed 

 among the Protozoa, forming the Order 

 Gregarinida ; but there are still doubts as 

 to their structure and nature. 



They exist as parasites within the bodies 

 of animals, and often inhabit the intestinal 

 canal, or the cavity of the abdomen. Most 

 frequently they are met with in insects, 

 especially their larvae ; but sometimes also 

 in Annelida, both freshwater and marine 

 (Lumbricus &c.), in the Crustacea and Mol- 

 lusca ; and even in human organs. 



They are mostly microscopic, and colour- 

 less ; round, oval, fusiform, or cylindrical 

 (PL 21. figs. 25, 28, 34) ; and consist of a 

 smooth transparent cell-wall, enclosing a 

 granular, more or less liquid mass, with one 

 or more nuclei or nucleoli. Sometimes 

 they exhibit a constriction in the middle, 

 or are divided by a transverse septum. In 

 some a process resembling a head is situated 

 at one end ; this may be short, round, and 

 obtuse or pointed, or more elongated and 

 furnished with reflexed hook-like processes. 

 The GregarincB are capable of motion, which 

 is either that of slow progression, ensuing 

 without contraction of the body, or pro- 

 duced by irregular contraction of the mem- 

 brane or substance of the body. 



Vibratiie cilia have been detected both 

 upon the outer and the inner surface of the 

 membrane ; and the internal granules often 

 exhibit molecular motion, especially after 

 the addition of water. One or more long 



