890 SUMMARY OF CURRENT RESEARCHES RELATING TO 



connection. To remedy tins a piece of the sponge is placed on a 

 slide covered with some drops of eau de javelle and left to stand 

 with a glass over it, until all the soft parts are dissolved, which, 

 in the case of thin sections, does not take more than 20-30 minutes. 

 Gemmules take a longer time and should be left over night ; their 

 contents are dissolved without destroying the outer coat. 



When the protoplasm is all dissolved the object is carefully 

 treated with acetic acid which removes all precipitated matters, then 

 with weak and afterwards with absolute alcohol. Finally oil of 

 cloves (which in 15 minutes completely clears any cloudy gemmules) 

 prepares the way for mounting in Canada balsam. The gemmules of 

 Spongilla fluviatilis, S. LieberJcuhnii, and S. contecta, from specimens 

 which spread out on the under side of stones, remain in situ between 

 the spicules, and give a perfect representation of the form of the 

 sponge. In the more compact sponges, such as the free growing 

 specimens of S. Lieberkuhnii, the spicules remain united to the 

 framework, although the lining and cementing substance has been 

 dissolved. The layer by which the sponge is attached to its support, 

 like the membrane of the gemmules, is not destroyed ; it is not, how- 

 ever, turned black, like the latter, with a solution of nitrate of silver. 

 These three elements of Spongilla have, therefore, a different chemical 

 composition. 



Diatoms are often found in the tissues of sponges, and these are 

 as well prepared by the above process as they are after burning or 

 boiling with sulphuric acid, so that eau de javelle is to be recom- 

 mended as a very useful reagent for diatoms also. 



To ascertain the effect on calcareous forms small mussel or snail 

 shells (with or without epidermis) were laid in eau de javelle. They 

 were clean and partly colourless but their lime remained uninjured. 

 The same was the case with the calcareous bodies from the crust of 

 different Gorgonidse. 



Small skeletons can be cleaned of skin, muscle, &c, without 

 injuring the bones. 



The liquid is also admirably adapted for cleaning vegetable 

 sections. Potash and glycerine swell up the cell-walls or break up 

 the preparations. In a quarter of an hour the sections are freed from 

 all the soft parts and show only the clear cell-walls. After treatment 

 with acet c acid they are mounted in Mayer's fluid (glycerine 1 vol., 

 distilled water 2 vols., and to 10 vols, of this mixture 1 part salicyl- 

 pyrogallic acid) or in gelatine-glycerine, balsam rendering the cell- 

 walls too transparent. 



Gum and Glycerine for Imbedding.* — L. Joliet has found that 

 the soap which he was in the habit of using for imbedding, and which 

 succeeded perfectly with the Salpce, gave very bad results with 

 Pyrosorna. It did not penetrate the common transparent substauce 

 which envelopes all the ascidio-zoids, so that they were rapidly 

 distorted, and could not be cut. The following combination has, 

 however, been of the greatest use : — 



* Arch, de Zool. Expe'r. et Gen., x. (1882) pp. xliii.-v. 



