ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 359 
may be composed of very different substances, just as the membrane of 
a cell may be. The present paper is apparently preliminary to others 
on the same subject. 
Structure of Retina.* * * § — Prof. A. S. Dogiel obtained very successful 
results by using a methylen-blue method. The retina must be laid on 
the slide with the nerve-fibre-layer turned towards the observer, and so 
that some quantity of vitreous humour remain associated with it. The 
methylen-blue solution must not come into direct contact with the retina. 
A solution of 1/10-1/16 per cent, solution, acting for 20-40 minutes, 
suffices to affect many nerve-cells of the inner and middle ganglionic 
layer. The preparation must be fixed on the slide with five to six drops 
of picric-acid-ammonia solution, to be followed by a mixture of glycerin 
and the aforesaid solution. After standing thus for 18-20 hours, the 
preparation may be closed up in the mixture named. 
Demonstration of Leucoplasts. j — Mr. L. S. Cheney recommends the 
leaf-stalk of Musa Ensete as a favourable object for examining leuco- 
plasts, all the stages in the development of the starch being easily fol- 
lowed. The leucoplasts are seated in the middle layers of the diaphragms 
which divide the intercellular passages of the leaf-stalk. 
C3) Cutting-, including- Imbedding- and Microtomes. 
Improvement to the Reichert Microtome.^ — Dr. J. Starlinger 
describes an improvement which, at his instigation, the firm of Reichert 
have made in their microtome (fig. 71). This improvement consists in the 
replacement of the free-hand movement of the knife-block by a mecha- 
nical movement. This is effected by a wheel, with which is connected a 
toothed wheel in whose teeth the links of a chain exactly fit. The 
chain passes over another wheel (with no teeth) at the other end of 
the instrument, and both ends of the chain are attached to the block. 
While one wheel is fixed, the other is adjustable with a screw, so that 
sufficient tension can be given to the chain. The second wheel is fixed 
by a clamp. By these means the friction is reduced to a minimum, and 
the movement is very smooth. 
Watch-Glass Imbedding Method.§ — Mr. A. B. Lee, in reply to 
Rhumbler, who described a method of imbedding small objects in watch- 
glasses, says that the method is a very old one, having been published 
in 1885 by Graf Spee, and employed by the writer for years most ex- 
tensively. For small objects he has found it the best process of any. 
It is not necessary to prepare the watch-glass with either glycerin or 
clove oil. After cooling, blocks can be readily cut out by means of a 
slightly warmed knife. Good paraffin does not break in the process. 
Apparatus for Stretching Paraffin Sections. || — Dr. J. Nowak uses 
an apparatus, constructed on the principle of the thermostat, for 
* Arch. f. Mikr. Anat., xlvi. (1895) pp. 391-113 (1 pi.). 
f Bot. Gazette, xx. (1895) p. 81. 
X Zeitschr. f. wiss. Mikr., xii. (1896) pp. 295-9. 
§ Tom. cit., pp. 157-8. 
|| Zeitschr. 1'. wiss. Mikr., xii. (1896) pp. 117-9 (1 fig.). 
