702 SUMMARY OF CURRENT RESEARCHES RELATING TO 



containing a few drops of Canada balsam (undiluted), and placed over 

 a spirit-lamp at such a hoight as to molt without danger of burning 

 tho balsam. In about a quartor of an bour tbo balsam has driven 

 out tbo clarifying agent, and penetrated tbroughout the entire 

 structure of tbe animal. A singlo drop of balsam is now placed on a 

 glass slip, and heated until it cools bard. Now take up tbe animal, 

 together with a bead of balsam, on tbo point of a needle, and place it 

 on the balsam on tbe slido, previously warmed, and prop it up in 

 such a position tbat tho plane of the sections desired may be parallol 

 to that of the slide, holding it thus until tbe balsam has cooled 

 sufficiently to keep it so. 



Tbere is just one consistency of balsam at which it may be readily 

 sliced witb a razor, witbout sticking to tbe blade, and yet is not 

 brittle ; and it is this condition which it is desired to obtain for tho 

 bead on the slide. Accordingly, when quite cold, it sbould be tested 

 with tho edge of a scalpel. If too soft, the slide must be warmed 

 over a lamp for a wbile ; if too hard, it must be removed from the 

 slide and replaced in tbe watch-glass, to which a drop of fresh balsam 

 has been added. In the difficulty of obtaining exactly the right 

 consistence lies the uncertainty of the method ; but when tbis is hit 

 upon successfully, really beautiful sections can be most easily 

 obtained by slicing down the bead with a sharp razor or lancet, as 

 in the ordinary hand method. The sections may be allowed to fall 

 from the razor on to the slide until all the material is exhausted, and 

 tben covered with dilute balsam under a large cover-glass, or they 

 may be picked up one by one on tbe point of a needle, and arranged 

 in order on a separate slide, wbich has been varnished with a thin 

 ccat of balsam so as to retain tbem in their respective places wbile 

 mounting. Tbe method is also useful for obtaining sections of 

 coralline Alga3, whose structure, when deprived of their lime, is so 

 rotten that it is extremely difficult to mount even tbe smallest sections 

 wbole, unless supported by some exceptionally firm imbedding 

 material. 



Preparing Echinodermata.* — Dr. 0. Hamann obtained good 

 fixation witbout undue contraction by injecting the somatic cavity of 

 Asteridea with a 1 per cent, chromic acid solution. When injected 

 tbe animals are to be placed in a vessel containing a similar fluid. 

 Good results were also obtained from a 1 per cent, cbromic acid 

 solution to which a few drops of a 1 per cent, osmic acid solution 

 had been added, and also from Kleinenberg's picro-sulpburic acid. 

 These acids are also advantageous, because they slowly decalcify the 

 star-fishes and therefore render tbem more amenable to the sublimate 

 solution. By the use of boiling w ater the ambulacral feet may be 

 obtained in their extended position, while preservative media penetrate 

 only slowly and irregularly within the substance of the body. 



For staining, the author used Ranvier's picro-carmine, also a 

 neutral (acetic acid) carmine, Bohmcr's hematoxylin, and also 



* 'Beitrage zur Histologie der Echinodermen, Heft 2, Die Asteriden,' 

 120 pp., 7 pis. and 3 figs., 8vo, Jena, 1885. 



