700 SUMMARY OF CURRENT RESEARCHES RELATING TO 
phuric acid, and partly in corrosive sublimate. A few larvae were also 
killed in Flemming’s solution. The sublimate specimens gave the best 
results. Picrocarmine was found to be the best staining reagent, as, 
being a nuclear stain and not affecting the yolk-granules, it made 
observation comparatively easy. 
Preparing Liver of Gastropoda and the Reconstruction of Organs.* 
• — For his observations on the morphology of the liver of Gastropoda, 
Dr. H. Fischer made use of sections of embryos ; these were imbedded 
in paraffin and previously fixed with saturated aqueous solution of 
sublimate, with alcohol or with picrosulphuric acid. This method, 
though not altogether irreproachable from a histological standpoint, is 
quite satisfactory for morphological purposes, as it not only allows of 
thin sections being made, but of the object being reconstructed from 
them. In reconstructing an object it will be found very useful to draw 
with the camera the outlines of the embryo after it has been fixed, as the 
possession of this contour renders it easier to reconstruct the object 
from drawings of its sections. 
The usual method of reconstructing a model of the object in relief 
is to make copies of the different sections in wax. Each wax plate 
should have a thickness equal to the product of the thickness of the 
section of the enlargement of the drawing. The outline of the object 
of each section is then drawn on these plates with the camera, and then 
the superfluous parts cut away. The plates having been joined together, 
an enlarged model of the original object is obtained. 
It is very important that the sections should be kept in series, or 
that some method for finding out the proper position of the individual 
plates should be adopted. If there be no possibility of doing this from 
the shape of the object or of its component parts, then marks must be 
placed on the surface of the paraffin block. These marks may be made 
by scratching a shallow furrow on one or more faces of the block, or by 
including a hair. The former is better, as some colour, e. g. black lead, 
may be worked in. 
When the organs are very thin or of very irregular shape, wax 
models are too fragile, but the difficulty may be avoided by cutting out 
the organs to be represented from the plate, so that the organ is repre- 
sented by a cavity, and this may be reproduced, after the model is 
finished, by means of a plaster cast. 
Investigation of Hephridia of Prosobranchs.f — Dr. R. v. Erlanger 
dropped living specimens of Patella and Fissurella into Kleinenberg’s 
picro-sulphuric fluid with a few drops of osmic acid, or into a mixture 
of sublimate 5 per cent, in sea-water 3 parts and 1 part of glacial 
acetic acid. Flemming’s chromosmic acetic fluid was found to make the 
tissues too brittle. In Trochus it was necessary to use a different 
method, on account of the stout shell and operculum. The specimens 
were, therefore, put into sea-water and 1 per cent, absolute alcohol in 
order to draw the anterior half of the body out of the shell. After a day 
or two the animals are paralysed without being killed. The fixing 
* Bulletin Scientifique de la France et de la Belgique (Extr. from), xxiv. (1892) 
87 pp. (7 pis.). 
f Quart. Jouru. Micr. Sci., xxxiii. (1892) pp. 589-91. 
