V. 



The Use of Formalin as a Preservative 

 Medium for Marine Animals. 



EARLY in the present year, my attention was drawn to the use of 

 Formahn as a preservative fluid, by a short account of some 

 experiments carried on by Professor Paulino de Oliveira^ at the 

 University of Coimbra, Since then, I have conducted in the 

 laboratory of the Jersey Biological Station a series of very extensive 

 tests, having the action of the fluid in question under daily observation.. 

 As the original investigation was conducted by Professor de Oliveira 

 on rather restricted lines, and further, as my results differ considerably 

 from his, it may be useful to workers at other stations and elsewhere 

 if I bring together the chief of my methods and state the principal 

 results obtained. 



As to the nature of the fluid, it is sufficient to mention that 

 formalin is the name given to an aqueous solution containing 40 per 

 cent, of formic aldehyde. Its chief commercial use at present is as an 

 antiseptic, and from its great bactericidal powers it takes high rank 

 as such. 



As a fluid designed to preserve marine organisms permanently, 

 formalin is best used in an aqueous solution of strength ranging from 

 two to eight per cent., and while a two per cent, solution will in many 

 cases give satisfactory results, in practice I find it advantageous, in 

 order to avoid any risk, to employ no solution of less strength than 

 three per cent. Where the animal is bulky, or contains much water, 

 I prefer to use a five per cent, solution. Hence in the following notes, 

 unless otherwise stated, the strength employed must be understood to 

 be that last named. It is to be noted that these percentages are 

 calculated by considering the commercial fluid, formalin, as being of 

 full strength (100 per cent.), although really it is but a 40 per cent, 

 solution of the active principle. 



For convenience in referring 10 these methods, I will treat of the 

 various phyla and classes separately — 1 will also premise that the use 

 of formalin does uot do away with the employment of the ordinary 

 fixing agents if the object is wanted for histological purposes. For 

 dissection and museum purposes, there is, however, no need of other 

 fixation than the action exercised by the formalin itself. 



^ Aniuics de Sciencias NaUiraes, vol. 2, no. ii., p. G9. (Porto; 1S95.) {See sXto 

 Natural Science, vol. vi., p. 229, April; 1895.) 



