ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 



319 



The mineral chips were supportedjon platinum-pointed pincers fastened 

 to a stand, and in this way brought within the focus of a low-power 



Fig. 82. 



objective. By means of a small gas-jet the mineral could be brought to 

 a white heat in a very short time, " without perceptibly warming the 

 objective and nicol." 



Capillary Tube Slide and Perforator of Cell-elements.* — One of the 

 principal drawbacks in the microscopical examination of small objects con- 

 sists in the difficulty of suitably orienting them on the slide in order to 

 observe successively all their aspects. In observing, for instance, the 

 segmentation of an ascidian ovum, the vitellus of which measures scarcely 

 more than • 1 mm., the turning round of such a delicate object demands 

 much patience, and leads only too often to its destruction. M. L. Chabry 

 therefore proposes the following apparatus : — 



The egg is sucked into a capillary glass tube having very thin walls, 

 and an internal diameter exactly equal to that of the egg, and measuring 

 8-10 cm. in length. A drop of sea- water introduced at the upper end of 

 the tube, held vertically above the liquid, induces an internal current which 

 drives the egg towards the middle of the tube. There is also required an 

 ordinary slide, to which are fixed with wax two small glass sockets, at a 

 distance sufficient to admit a cover-glass between them. These two sockets, 

 which lie in a line following the long diameter of the slide, so exactly admit 

 the capillary tube, that they permit no other movements than of rotation 

 and of sliding longitudinally. That part of the tube lying between the 

 two sockets, and containing the egg, is covered with a thin cover-glass, 

 beneath which a drop of water is introduced. Thus submitted to micro- 

 scopical examination, the object presents a clear image and its rotation is 

 determined, even beneath the observer's eye, by the rotation imparted to 

 the capillary tube. In order to have the latter under perfect control, 

 one of the ends projecting over the edge of the stage is bent like the 

 letter L. 



To make it serve as a pricking, perforating, and injecting instrument, 

 there is introduced into the capillary tube a very fine glass thread, ter- 

 minated by a short, sharp point. If the end opposite that through which 

 the stylet has been introduced be closed in such a manner as to prevent any 



* Comptes Eendus Soc. Biol., iii. (1886) pp. 322-3. 



