470 SUMMARY OF CURRENT RESEARCHES RELATING TO 



hue of the internal juices of the insects. These cannot be preserved 

 by balsam, but it is otherwise with the pigments which stain the 

 somewhat horny coverings of the thorax and abdomen. These colours 

 are persistent." 



Breckenfeld's Method of Mounting Hydrse.* — A. H. Breckenfeld 

 describes the following process as accomplishing the desired end 

 more perfectly than any other published. 



Have in readiness a slide upon which a well-dried cell of sufficient 

 depth has been turned. Then, from a gathering of Hydra, transfer a 

 sufficient number of individuals (the more fully developed the better) 

 very carefully, by means of a camel's hair brush or a pipette, to a drop 

 of water spread near the end of a plain glass slide, and place the 

 latter upon a table in such a way that the end with the drop projects 

 about two inches over the edge. This is easily done by placing a 

 weight upon the opposite end. After allowing the slide to remain 

 perfectly undisturbed for three or four minutes, hold a lighted coal-oil 

 lamp so that the top of its chimney is very near the slide, but a trifle 

 above it. The Hydrce will then appear brightly illuminated, and it 

 can easily be determined by the unaided eye whether or not their 

 tentacles are fully extended. If they are, quickly move the lamp 

 directly under the drop, with the top of the chimney about an inch 

 beneath the slide, and hold it in that position for about 3-5 seconds, 

 the exact time depending principally upon the intensity of the heat. 

 Then quickly remove the slide and place it upon a slab of marble or 

 metal. When cool, pour the drop containing the zoophytes into the 

 prepared cell on the elide which has been held in readiness, add a 

 drop or two of a suitable preservative fluid, arrange the animals, if 

 necessary, by means of a needle or camel's hair brush (using very 

 great care, however, as the tentacles will be destroyed by the least 

 rough handling), cover with thin glass, and finish as in the case of 

 any fluid mount. 



This " hot water " process seems to succeed peculiarly well with 

 the brown Hydra {H. vulgaris). 



Cell-sap Crystals-f^ — Crystals of the colouring material present in 

 the petals and other portions of plants are by no means common or, 

 as a rule, easy to obtain ; and G. Pim thinks it may therefore interest 

 some to know that the rich violet-coloured cell-sap in the flower of 

 Justicia speciosa, a common and easily-grown stove-plant, crystallizes 

 very easily into minute slender prisms. To obtain them it is only 

 necessary to mount a fragment of the flower-stamen for choice, in 

 dilute glycerine jelly, not too hot, withoiit any previous treatment ; 

 after a few hours the colouring material collects into a few cells, in 

 the form of the crystals above mentioned, forming a very pretty and 

 interesting object for a 1/4 in objective. 



Staining for Microscopic Purposes.^ — H. Gierke contributes a 

 paper on this subject. In the first part, after an excellent introduc- 



* Amer. Mon. Micr. Journ., v. (1884) pp. 49-50. 

 t'Journ. of Bot., xxii. (1884) p 124. 



t Zeitschr. f. Wiss. Mikroskopie, i. (1884) pp. 62-100. See Bot. Centralbl., 

 xviii. (1884) p. 52. 



