140 



HARDWICKE'S SCIENCE-GOSSIP. 



S [June 1, 1870. 



MICROSCOPY. 



Scale or Tench. — The scale of this sullen fish 

 {Tinea vulgaris)\is of such a marked character, and 

 differs so essentially from those of other fresh-water 

 fishes, already figured in this journal, that our 

 readers 'will lose uo opportunity of adding such a 



#1 



t 



11 



■\l 



mmmm 



ig. 131. Scale of Tench. 



slide to their collections. Generally this scale is 

 absent from cabinets, as though it had no character 

 of its own ; but our figure will, we hope, redeem the 

 Tench, and its scales, from any such imputation. It 

 is magnified to the same extent as former examples. 



HOW TO TREPARE YOUNG OYSTERS FOR THE 



Microscope. — Acting on the principle I always ad- 

 vocate, that there should be no secrets in science, 

 I feel much pleasure in offering to " W. J. B." the 

 information he desires respecting the method of 

 cleaning the shells of young oysters. It is not im- 

 probable that those of which he expresses approba- 

 tion passed through my hands, for I presented some 

 time ago a quantity of them to one of our leading 

 opticians, who has them mounted as he requires 

 them for sale. Having found a "black-sick" oyste r 

 (to use the dredgermen's term), the spawn of which 

 |s quite mature and ready for extrusion, pour off 

 from the shell the dark slate-coloured fluid into a 

 long narrow two-ounce phial ; fill up the bottle with 

 distilled water ; shake it up gently ; allow the 

 deposit to settle, and change the water two or three 



times, repeating the agitation to get rid of the salt. 

 Then substitute for the water liquor potassce, diluted 

 with an equal quantity of distilled water. Allow the 

 young oysters to remain in this for two days, agita- 

 ting occasionally ; and, as often as the solution 

 becomes discoloured, pour it off, and renew the 

 same until no colour is given off and the shells are 

 seen to be thoroughly cleansed from all animal mat- 

 ter, by their sinking freely and rapidly to the 

 bottom. When this stage is arrived at, stop the 

 process, that the two valves of the shells may not be 

 separated by the destruction of the hinge. Wash 

 repeatedly in distilled water, to remove all trace of 

 the alkali, and finally wash and preserve the shells 

 in a little rectified spirits of wine (not methylated 

 spirit). When they are to be mounted for the 

 microscope, shake them up with the small quantity 

 of spirit ; and, before they settle, dip in a fine camel- 

 hair brush, and deposit its contents on the slide. If 

 too much spirit has not been added to them, there 

 will be just enough of the shells in the brush to 

 make a nice object. They show better when not 

 huddled together too thickly. If undistilled water 

 or methylated spirit be used, instead of being 

 brilliant and clean, the shells will probably have the 

 milky and semi-opaque appearance which is so ob- 

 jectionable. As each oyster produces on an average 

 eight hundred thousand young ones, the spawn of 

 one parent will be sufficient for almost any number 

 of slides. It is worthy of notice that, in its early 

 condition, the oyster has both valves equally convex* 

 This process is equally applicable to the bleaching 

 and preparation of starfishes. — Henry Lee. 



Note on Diatoms. — While examining the 

 linear fronds of the common Ulva (U. elongata), 

 my attention was directed to an indistinct bundle 

 of motion far down in the depths of the surround- 

 ing water. I removed the half-inch objective in 

 use, and substituted the quarter-inch, when I im- 

 mediately recognized that marvel of anomalies, the 

 Bacillaria parado.ra. I should think the specimen 

 (if I may so term it) was unusually large and 

 perfect. In shape I can compare it to nothing 

 better than a "villus" of the human intestinal 

 membrane covered with minute spines, while the 

 inexplicable never-ceasing motion of the number, 

 less frustules put me in mind of a quantity 

 of small, short needles, thrown carelessly together, 

 and irregularly agitated by changing the poles of a 

 battery in connection. In fact the presence of 

 electric currents as affecting the arrangement of 

 the frustules seemed more than probable, for when 

 a portion of the bacillaria occasionally separated and 

 gradually spread out into a projecting limb, the 

 frustules invariably returned to their normal posi- 

 tion by an end-to-end-like motion, one over the 

 other, as if alternately attracted and repelled by 

 chemical currents. — Walter B. Cole, Weymouth. 



