446 S. F. Harmer. On a method for the Silver staining of marine objeets. 



where F. E. Schtlze first has been unable to detect a cell layer of 

 tbis kind. even by tbe use of silver niti'ate^ : in Thenea. where Sollas2 

 has observed no eell-ontlines , and in many other Sponges. Dr. Ed. 

 Meyer has successfully applied the same method to the epidermis and 

 peritoneal epithelium of Annelids Tomopieris . Amplàctenidaé . to Te- 

 /eosYea/iOva, etc. He has obtained good nuclear colouration by trans- 

 ferring the tissue after reduction in potassio nitrate to alcohol. and sub- 

 sequently staining with Mater's alcoholic Carmine 3. In Brachiopoda, 

 Dr. J. F. VAX Bemmelex has had no difficulty in using the method for 

 the investigation of the epidermis and peritoneal epithelium. 



Few animals seem to resist the action of potassic nitrate to so great 

 an extent as Loxosoma and Pedicellina. most forms being either imme- 

 diately, or after a few minutes . killed by an immersion in a 5 per cent 

 solution of this substance. Even in many of these cases. the tissues 

 suffer very little histological change. and can be easily stained by silver 

 nitrate. It is possible that many other salts may be used more advan- 

 tageously than potassio nitrate in washing the chlorides from the tissues 

 wlthout killiog the animai. A 4^ o P^r cent solution of sodic sulphate 

 may be used instead of the potassic nitrate . over which . however . in 

 most cases it has no obvious advantages. 



R. Heetwig^ has described a method for the Silver staining of 

 marine animals . consisting in treating with dilute osmic acid , washing 

 with distilled water . until the chlorides are removed . subsequently 

 placing in a silver nitrate solution, and reducing in distilled water. By 

 this method . Hertwig has been able to obtain sharply defined celi 

 limits in the ectoderm of Ctenophora . but not over the whole surface 

 of the epithelium. I bave myself employed HERT'^riG's method in Loxo- 

 soma and Pedicellina . but with results not nearly so satisfactory as in 

 the method I bave described. the limits of the epidermic cells being not 

 visible over the whole surface. whilst after the employmeut of Dr. Ran- 

 soii's method in these two genera . I bave invariably found that every 

 epidermic celi was distinctly marked out by a sharp contour. 



Xaples, July 9, 1SS4. 



1 Zeitschr. f. wiss. Zool. Bd. XXIX, p. 107 and Bd. XXXI, p. 290. 



2 Ann. and Mag. of Nat. Hist 5th Series, Yol. IX, p. Uh. 



3 Mittheil. a. d. Zoolog. Stat. zu Neapel. Bd. lY, p. 521. 

 * Jenaische Zeitschr. Bd. XIV, p. 324. 



