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PBOTOCO'CCUS NIVA'LIS. The name 

 given to an extremely minute plant 

 which grows upon the surface of 

 the snow in certain regions, im- 

 parting to the snow a red appear- 

 ance, from which circumstance it 

 was at first supposed that the snow 

 itself was red. Mr. Darwin, in his 

 account of his passage of the Cor- 

 dillera of the Andes, thus describes 

 it: "On several of the patches of 

 perpetual snow, I found the Pro- 

 toccocus Nivalis, or red snow, so 

 well known from the accounts of 

 Arctic navigators. My attention 

 was called to the circumstance from 

 observing the footsteps of the mules 

 stained a pale red, as if their hoofs 

 had been slightly bloody. I, at 

 first, thought it was owing to dust 

 blown from the surrounding moun- 

 tains of red porphyry, for from the 

 magnifying power of the crystals 

 of snow, the groups of these atom- 

 like plants appeared like coarse 

 particles. The snow was coloured 

 only where it had thawed rapidly, 

 or had been accidentally crushed. 

 A small portion of it rubbed on 

 paper communicated a faint rose 

 tinge, mingled with a little brick- 

 red. I placed some of the snow 

 between the leaves of my pocket- 

 book, and a month afterwards ex- 

 amined with care the pale disco- 

 loured patches on the paper. The 

 specimens, when scraped off, were 

 of a spherical form, with a diameter 

 of the thousandth of an inch. The 

 central part consists of a blood-red 

 substance, surrounded by a colour- 

 less bark. "When living on the 

 snow they are collected in groups, 

 many lying close together. The 

 dried specimens placed in any fluid, 

 as water, spirits of wine, or diluted 

 sulphuric acid, were acted on in 

 two different ways : sometimes an 

 expansion was caused, at others a 

 contraction. The central part after 

 immersion invariably appeared as 

 a drop of red oily fluid, containing 



a few most minute granules ; and 

 these probably are the germs of 

 new individuals." 



PKO'TOGINE. A term applied by the 

 French to the talcose granite of 

 the Alps. The name given to a 

 granite composed of felspar, quartz, 

 and talc or chlorite ; the talc sup- 

 plying the place of mica. Protogine 

 is distinguished from granite not 

 only in the substitution of talc for 

 mica, but also in its great tendency 

 to disintegration. Dr. Boase di- 

 vides protogine into five species, 

 namely, porcelainous, shorlaceous, 

 fluoric, porphyritic, and quartzose. 

 These are all found in Cornwall. 



PBOTOZO'A. A sub-kingdom of ani- 

 mals comprising the two classes, 

 Stomatoda and Astomata. 



PBOTOZO'IC. (from Trpwros, first, and 

 uW, animal, Gr.) A name pro- 

 posed by Sir E.. Murchison to be 

 given to those rocks which are 

 supposed to contain the remains of 

 the first formed animals or vegeta- 

 bles ; the first or lowest formations 

 in which animals or vegetables 

 occur. " That there is a limit in 

 the descending scale of formations, 

 beneath which no traces of life 

 have been discovered, is now pretty 

 generally recognized ; and looking 

 merely to this fact, geologists may 

 agree to use the term Protowic y 

 however they may differ in their 

 interpretation of the phenomenon." 

 Sir It. MurcJdson. 



PBI/INOSE. (from pruina, Lat. a 

 frost, or rime.) In entomology, 

 applied to the clothing of insects 

 when covered with a minute dust, 

 scarcely discoverable by the lens. 



PSAMMO'BIA. A small bivalve found 

 in the cyclas limestone of Burwash. 



PSAHMO'STEUS. A genus of ichthyo- 

 lites of the old red sandstone, of 

 which Agassiz, in his Poissons 

 Fossiles, describes four species. 



PSEU'DO. (^eo9, Gr. false.) A 

 term generally used as a prefix to, 

 and in composition with, other 



