SOME HINTS ON COLLECTING SPECIMENS. 401 



" ful of formalin. After lying in this for two or three days only, 

 " take them out and wipe them with a dry cloth ; again clean bottle and 

 u place minnows with same quantity of water and one-half teaspoonful 

 " of formalin, sealing up bottle airtight with wax." A German corre- 

 spondent of the same paper recently explained that he kept his minnows 

 in the pure formalin for a week and then changed them to a 4 per cent, 

 solution for another week, after which he put them into an empty bottle 

 tightly corked with ouly a few drops of formalin. He found that they 

 kept in this dry form quite well for two years. From what I can learn 

 it seems doubtful whether the change to a fresh solution after the first 

 few days is at all necessary. 



On the use of formalin as a re-agent I cannot do better, I think, 

 than quote from one of the bulletins issued by the Smithsonian Institute 

 (United States National Museum) on the methods employed at the 

 Naples Zoological Station for the preservation of marine animals, trans- 

 lated from the original Italian, as the opportunities for practically 

 testing it have probably been greater there than anywhere else. 



;i Formalin is a very useful liquid for keeping animals temporarily, 

 " but not for preserving them permanently. Some pelagic animals — 

 " for example certain Medusae, Pterotrachaidse, and Salpidse — may 

 " remain in it for even two or three years without serious detriment, 

 " but if they are not transferred to alcohol by that time they begin 

 " to disintegrate or decompose. Formalin therefore may be used on 

 u a voyage or a long journey when alcohol is scarce or not to be 

 " had. As a provisional fluid it is useful for many animals which are 

 " not contractile, and especially for those which contain no lime spi- 

 u cules, skeleton or shells. ... In the case of large animals, such 

 " as fish, one must make an injection through the anus of a solution 

 " of at least 5 per cent, strength. For animals of some consistency, 

 " like fish and ascidians, one should use a 2 to 6 per cent, formalin 

 " solution, the general rule being that the softer the animal the weaker 

 " the formalin. . . . It is not necessary to wash objects which 

 " have been in formalin before transferring them to alcohol, . . . 

 " Colours certainly are preserved for a longer time in formalin than 

 li in alcohol, but in time those which are fugitive in one disappear in 

 '' the other also. The preservative medium has not yet been discovered 

 " which will permanently preserve the colours which are due to a pig- 

 " ment in the skin or substance of an animal." 



Specimens of the larger fishes — such as sharks, rays, &c, that are 

 too big to be preserved in spirits must of course be skinned and as my 



