200 



HARDWICKE'S SCIENCE-GOSSIP. 



MICKOSCOPY. 



Mickoguapiiic Dictionary.— The attention of 

 our microscopical readers is directed to the fact 

 that a new edition of the well-known " Micrographic 

 Dictionary" is now in course of publication by 

 Van Voorst, in monthly parts, of which two have 

 already appeared. This work is too well known to 

 require commendation, and is, in fact, not only a 

 standard book, but the only one of the kind at all 

 comprehensive in character. 



Amplification (p. 236).— "E. A. E.'s" remarks 

 are certainly not uncalled for, more especially as a 

 variation of magnifying power frequently alters the 

 appearance of an object so entirely as to make it 

 unrecognizable ; but, even when the magnifying 

 power of an instrument tallies approximately with 

 that of a given engraving, it but too often happens 

 that a large allowance must be made for the imagi- 

 nation of the artist, who fills in the details according 

 to his idea ; also difference in size, &c, must be 

 allowed for, as illustrations would naturally be made 

 from the best and most perfect specimens obtain- 

 able, which may be beyond the reach of the talent 

 or purse of the amateur. — & P. P. 



Scale of Perch. — Although on a fomer occa- 

 sion we gave an illustration of this favourite fish- 

 scale, it was not on the whole satisfactory, and 

 would not compare with the scales recently figured, 

 in point of art. "We have now produced a more 



Nostoc. — Surprise has been excited in the minds 

 of some of our correspondents on account of a green 

 gelatinous substance found recently, after rainy 

 weather, upon grass, gravel walks, &c, and which 

 some have supposed to be a fungus. This is really 

 one of those curious organisms which the scientific 

 call Nostoc, and which they refer to the Alga?, or 

 family of Water-weeds. There are several species 

 of them, and five or six have been found in Britain, 

 one or two being purely aquatic. The internal 

 structure in all is remarkably alike, consisting of 

 beaded, undulating threads, immersed in gelatine. 

 There is a great deal connected with the life-history 

 of these bodies which requires working out, and 

 many points deserve study and investigation. It 

 will be observed, on examining the substance with a 

 quarter-inch objective, that the threads are made up 

 of a series of spherical bodies, which are coloured, 



Fig. 154. Scale of Perch. 



worthy portrait of this scale, which has so deserv. 

 edly obtained a name and place in almost every 

 rollection, and with it we fear that our examples of 

 the scales of fresh-water fishes have almost come to 

 ;m end. 



Fig. 155. Nostoc commune, nat. size. 



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8 W^ 



c 



n dr? o (J ^oSoc&tA P P, ° ^' 

 8°9, 1 °In -co^ooq^^cP J&° 



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Qn 00^000 qS^^-cPrpo ?-, 



Fig. 156. Nostoc commune, x 320. 



and slightly attached to each other, like beads on a 

 string. Here and there one sphere is larger than 

 the rest, and often these larger spheres are also free 

 from the threads, amongst the gelatine. It is more 

 suspected than really known that these larger bodies 

 are concerned in the'reproductive process, and that 

 they are sporangia, or something of that kind. Our 

 object now is to indicate that these green gelatinous 

 masses are called Nostoc commune ; that they have 

 constituted in some countries (China, for instance) 

 a portion of human food ; and that any one with 

 leisure will find in them an object worthy of study 

 and elucidation. 



