ZOOLOGY AOT) BOTANY, MICROSCOPY, ETC. 847 



especially for objects which are very delicate and very sensitive to 

 the effects of endosmosis. 



Chloral Hydrate for Preserving Tissues.* — Dr. W. W. Munson, 

 being often obliged to postpone the dissection or other preparation of 

 insects, &c., finds that putting a little chloral hydrate into the water 

 preserves all animal tissues perfectly, without hardening or otherwise 

 changing them, for any length of time. Five grains to an ounce of 

 water is strong enough for all small objects. 



Vegetable specimens may be kept fresh in the same way. The 

 solution must not be too strong, say only a grain or two to the 

 ounce. 



Chalon's Microscopic Finger. f — Under the title of " Arrangement 

 des Diatomees pures," J. Chalon describes an apparatus for picking up 

 diatoms out of a mixed gathering, which, as he rightly says, " in 

 default of any other merit possesses at least that of simplicity." 



To a thin piece of deal 15-20 cm. long a hog's bristle of 4-5 mm. 

 is articulated by means of a spherule of lead (a large shot) held 

 between two brass rings. It forms, therefore, a lever with unequal 

 arms, the wood one part and the bristle the other. The spherule is 

 the fulcrum. 



Any movement given to the extremity of the long arm of the lever 

 becomes very slight and also reversed at the end of the bristle, so that 

 in working with a power of 50 to 60 diameters the bristle seems, 

 under the objective, to have a direct motion and an ordinary speed. It 

 might be easily supposed that a needle was being used with a simple 

 lens. 



The apparatus is fixed to the stage by a clamp. If it is 

 attached to the fixed part of a mechanical stage, great facility would 

 be given for bringing any desired object under the point of the 

 bristle. With a little experience 30 to 40 diatoms can be arranged in 

 an hour. 



Mounting Opaque Objects.l — Professor A. H. Chester, in a paper 

 on this subject, says : — 



" In mounting opaque objects the chief difficulties to be overcome 

 are in fixing the object to the slide, and in preventing the cement from 

 running into the cell after mounting. After many trials I have 

 adopted the following method. The objects, if light, are attached by 

 means of a thin solution of gelatin. A little spot of the solution is 

 dried on the slip, and the objects are then placed upon it and attached 

 by breathing on the slide. This is then allowed to remain on the hot 

 plate until all moisture has been driven out. If a heavier object is to 

 be mounted, a circle of Brunswick black is turned on the centre of the 

 slip, which is then placed on the hot plate until so hard that the object 

 will not sink into it. It is allowed to cool, the object placed in posi- 

 tion and fixed by heating for a moment over the lamp. If just the 



* Amer. Journ. Micr., vi. (1881) pp. 117-18. 

 t Bull. Soc. Belg. Micr., vii. (1881) pp. cxx.-i. 

 X Amer. Journ. Micr., vi. (1881) p. 125. 



3 K 2 



