ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 705 



transparent diatoms, between dry mounts and those in monobromide. 

 The markings of P. angulatum are almost invisible in balsam, but in 

 tbe monobromide tbey are as readily seen as on the dry frustule, and 

 also the same peculiar colour of the dry valve. Ampliipleura pellucida 

 is quite as distinct and easily resolvable as in a dry mount. Herr 

 Weissflog adds that the distinctness of the diatoms as compared with 

 the balsam mounts is very great, and is especially noticeable in 

 jRMzosolenia. 



Mounting Marine Algse.* — The Eev. J. D. King says that the 

 best medium for preserving the colour, either of marine or fresh algae, 

 so far as he has tried it, is a preparation suggested by Dr. Munson, of 

 Otisco, N.Y. : chloral hydrate, 15 grains ; water, 2 ounces. 



The tendency of this fluid is to make objects preserved in it more 

 transparent ; but he has slides of green algae mounted a year ago, 

 which yet retain the brilliancy of living colours, and appear in striking 

 and favourable contrast with those mounted in other media. It needs 

 a further trial before pronouncing safely upon its merits, but he 

 believes it to be worthy the attention of algologists. 



Mounting Starches.j — Mr. E. Hunter considers that the method 

 described at page 536 is not a good one, as heat alters the form of all 

 starches. When required for polariscope objects, thin dammar and 

 thin balsam are perhaps the best media, used cold and left to harden 

 spontaneously. By this, wheat-starch and many others which do not 

 polarize under ordinary circumstances show well. For ordinary exami- 

 nation, weak solution of ammonia is one of the best media. 



It is also pointed out ij that an excess of heat will cause the granules 

 to burst and disappear. 



Mounting Opaque Objects with Beeswax.§ — Mr. H. Morland 



gives some suggestions for mounting opaque objects. 



He melts down in an oven bleached beeswax (in cakes) with ultra- 

 marine or vegetable black, stirring the whole well together. Too much 

 ultramarine must be avoided, as it will crystallize out on the surface of 

 the wax. The blue wax gives a most pleasing background for dead-white 

 objects, and the effect is enhanced by illuminating the wax from beneath. 



The wax is melted in a cell on the slide over a spirit lamp, when 

 it will form a cup-shaped bottom. It should be cooled quickly by 

 placing the slide on metal or marble. The objects are fixed not by 

 any cement, but by simply placing the slide upon a block of iron 

 heated to about 140° F. If the object is large it may require to be 

 slightly pressed into the wax. The objects appear by this method to 

 be merely laid on the surface of the wax, and there is no danger of an 

 objectionable " wall " ever appearing round the object if the cover has 

 been hermetically sealed with the wax (using white cement afterwards). 



The "wall" is generally caused either by the background not 

 being sufficiently dry or by the vapour of the solvents of the cements 



* Amer. Journ. Micr., vi. (1881) p. 58. 



t Sci.-Gossip, 1881, p. 135. t Ibid., p. 160. 



§ Journ. Quek. Micr. Club, vi. (1881) pp. 196-8. 



