2i8 DISCOVERY REPORTS 



For fixation lo per cent formalin and weak spirit were the reagents most commonly 

 employed. Speaking generally the formalin was used for soft-bodied animals and those 

 that had been anaesthetized, and the spirit for Sponges, Crustacea, Echinoderms and 

 other animals in which delicacy in tissue fixation was not required. The hardening 

 properties of formalin render it a most valuable reagent, and as a fixative it is to be 

 recommended even for animals with calcareous spicules, such as Alcyonaria and Holo- 

 • thurians, which if permanently preserved in it would be ruined. Fish and all mala- 



costracous Crustacea are best fixed in weak spirit, but even in these groups formalin 

 has its uses : deep-water pelagic species are frequently very soft and are much improved 

 by a preliminary hardening in formalin. For many delicate planktonic organisms a salt- 

 water solution of formalin was employed. This proved very satisfactory with Lepto- 

 cephoJus larvae, which always blister if fresh water is used. With some of the transparent 

 pelagic Polychaetes no success could be obtained with menthol, but they turned out 

 well if a little weak formalin was added to the salt water. Other Polychaete worms, when 

 fully anaesthetized, were straightened out with a brush on a filter paper saturated in 

 formalin, more formalin being added as soon as they had acquired sufficient rigidity. 



Special methods of fixation were adopted for certain animals and for those which 

 seemed to possess particular anatomical interest. Of these Bouin's fluid was most 

 frequently employed, and was very successful with a large range of organisms. It proved 

 excellent for the polypides of Gephalodiscus and it gave such good results with Diphyids 

 that it was adopted so far as possible as a routine method. Salps of soft consistency 

 were frequently fixed in Bouin and afterwards preserved in formalin. For Crustacea 

 and their larvae Bouin's formula was replaced by that of Duboscq, and for Turbellaria, 

 Cestodes and Trematodes one of the corrosive mixtures (Schaudinn or Petrunkewitsch) 

 was used. Hot 70 per cent spirit was used for the fixation of Nematodes. As recom- 

 mended by Lo Bianco, Crinoids were fixed by quick immersion in strong spirit and, 

 with some species at least, this appears to be the only method by which perfect specimens 

 can be obtained. With most of the Ctenophores indifferent success was attained; some 

 kinds could be fixed in formalin and transferred afterwards to spirit, while others, 

 though they shrank greatly in the process, gave moderate results with Bouin's fluid; 

 others, however, seemed to defy all attempts at preservation. 

 \ As permanent preservatives 10 per cent formalin and 75 per cent spirit were almost 



invariably employed. Most organisms were preserved in spirit, and those that had been 

 fixed in formalin were usually placed for a time in weak spirit before being transferred 

 to the stronger solution. To bring specimens through more gradations of spirit was 

 usually impracticable and it was only attempted with those that were of special interest. 

 Neutralized formalin was used as a permanent preservative for Medusae, Copepods, for 

 transparent pelagic animals such as Sagitta, Tomopteris and Carinaria, and for bulk 

 collections of plankton. The contents of large plankton nets were partially sorted on 

 board and the Crustacea, Cephalopods, fish, etc., preserved in spirit. 



The Alcohol used for making the 75 per cent solution was the ordinary commercial 



