528 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
(2) Preparing Objects. 
Preparation of Crustacea.* — Dr. 0. vom Rath gives an account of 
the method he adopted in his investigation into the structure of the 
Cymothoid Crustacean Anilocra mediterranea. The heads were cut off 
with a sharp pair of scissors and immediately placed in picric-nitric 
acid, picric-sulphuric acid, warmed absolute alcohol or chrom-osmic- 
acetic acid ; the first of these reagents gives especially good results. The 
hardened heads were stained in toto in alum-carmine or borax-carmine. 
Paul Meyer was quite right in urging that the mere preservation in 
alcohol of Crustacea or other Arthropods with a strong chitinous 
membrane is quite insufficient. 
Modes of Studying Segmental Organs of Hirudinea.f — M. H. 
Bolsius did not learn much by dissecting out the segmental organs and 
mounting them entire. It is better to cut sections of the entire animal, 
or, when it is large, of parts. Transverse, vertical, longitudinal, or hori- 
zontal longitudinal sections should be made. To prevent contraction 
of the body, large specimens should be anaesthetized before being killed. 
Small specimens should be placed in a 1 per cent, (or even weaker) 
solution of chromic acid. Passable results in the way of fixation were 
obtained by bichromate of potash, but bichloride of mercury is much 
more efficient. A saturated aqueous solution or Gilson’s liquid may 
be used. In either case small individuals are placed in them for 15 to 
30 minutes; larger pieces must remain a proportionately longer time. 
Excellent preparations were also obtained with a 2 per cent, solution of 
nitrate of silver ; in this case staining reagents were not used, but with 
the others a picro-alum-carmine, the formula for which has not yet been 
published, but which is used at Louvain, was found to give excellent 
results. 
Mode of Investigating Hydra fusca.J — Herr K. C. Schneider 
recognizes that it is only possible to study the nervous system of 
Hydroids by maceration-processes. It is scarcely possible to recognize 
in sections the cell-boundaries of the ectoderm, to say nothing of 
distinguishing them from the separate subepithelial elements. The 
structure of the cells is considerably affected by the use of paraffin. 
As a maceration-medium, the author first used pure acetic acid from 
1 to 10 per cent ; but as this caused deformation of the elements, 
chloride of sodium was used, and was followed by various strengths and 
quantities of osmic acid. After some experiments, a mixture of one 
part 0 * 02 per cent, osmic acid with four parts 5 per cent, acetic acid was 
found to give excellent results. Pure osmic acid was found to give very 
different results from the mixture of osmic and acetic acids. Animals 
placed for eight days or more in glycerin were very useful in the study 
of the nervous system. Picrocarmine was found to be the best staining 
medium, but Beale’s carmine and safranin were also of use. 
Microscopical Sections of Tooth and Bone.§ — It was with great 
satisfaction that we read Mr. J. Howard Mummery’s notes on the prepa- 
* Zool. Anzeig., xiii. (1890) p. 232. f La Cellule, iv. (1890) pp. 374-6. 
J Arch. f. Mikr. Anat., xxxv. (1890) pp. 322-3. 
§ Trans. Odontol. Soc. Great Britain, xxii. (1890) p. 207. 
