On a method for the silver staining of marine objects. 



By 

 Sidney F. Harmer, 



King's College, Cambridge. 



The principle of this method was suggested to me by Dr. W. H. 

 Ransom, and consists in the replacement of distilled water in the ordì- 

 nary process of silver staining by a solution of a neutral salt not pre- 

 cipitable by silver nitrate, and of the same specific gravi ty as sea water. 

 Loxosoma and PediceUina were the first objects investigated, and these 

 animals are not killed by an exposure of as much as half an hour to a 

 5 per cent solution of potassio nitrate in distilled water. It is thus quite 

 easy to free the tissues from the greater part of their Chlorides by wash- 

 ing with the above mentioned solution of potassio nitrate ; from this the 

 objects are transferred (naturally without the formation of any precipi- 

 tate) for 4 or 5 minutes to a solution of silver nitrate f'/s — 1 per cent, 

 according to circumstances) . After reduction of the silver during ex- 

 posure to light in the nitrate solution, the tissues may be mouuted per- 

 manently either in glycerine or in Canadabalsam. Very beautiful pre- 

 parations of Loxosoma were easily obtained by the use of osmic acid 

 and picrocarmine after treatment with silver nitrate. The animai may 

 either be transferred directly from the silver solution to osmic acid 

 (72 per cent) and thence to picrocarmine, reduction taking place during 

 the process , or the osmic acid may be added after the silver has been 

 already reduced in the potassio nitrate. In successful preparations made 

 in the above manner , the limits of all the cells of the epidermis and of 

 the alimentary canal are exceedingly sharply marked out, the nuclei of 

 these cells as well as of the muscle cells, connective tissue corpuscles 

 and other tissue Clements being very distinctly stained. Besides the 

 above mentioned forms, I have obtained good results with the epidermis 

 of 3Iedusae, Hydroids^ Sagitta and Appe7idicularia (tail) . 



Amongst Spotiges ^ Dr. G. C. J. Vosmaer has, by means of the 

 above method, easily demonstrated an outer epithelium in Chondrosia^ 



