BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [10] 



immersed directly in 70 per ceut alcohol, the liquid beiug changed after 

 a few days. Changes should be made until the alcohol remains color- 

 less. When an animal which has been in alcohol is transferred to that 

 which is stronger, it is necessary to agitate the jar from time to time to 

 avoid the formation of a layer of weaker alcohol on the bottom. 



Many liquids have been tried at the station in search for a possible 

 substitute for alcohol, but always with poor results. Some liquids, like 

 those of Goadby and of Owen, when used on gelatinous forms, eventu- 

 ally produce contraction and consequent distortion. Wickersheimer's 

 solution, which was highly praised when first brought out, distorts or 

 macerates marine animals. Alcohol of 70 jier cent is preferable for the 

 permanent preservation of animals for the reason that it is sufficiently 

 absorbed by the tissues after repeated changes. A stronger solution 

 not only is unnecessary for good preservation in the majority of cases, 

 but it is even harmful in some, because it eventually hardens the 

 objects too much and renders them brittle. Alcohol is useful, further- 

 more, for narcotizing animals and for killing them slowly or quickly. 



Formalin or formaldehyde. — Formalin is a very useful liquid for keep- 

 ing animals temporarily, but not for preserving them permanently. 

 Some pelagic animals — for example, certain Medus*, Pterotrachaidse, 

 and Salpid^TB — 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 a voyage or a long journey when alcohol is scarce 

 or not to be had. As a i)rovisional fluid it is useful for many other 

 animals which are not contractile, and especially for those which con- 

 tain no lime spicules, skeleton, or shells. Shell bearing mollusks, 

 echinoderms, and such things can not be preserved in formalin on 

 account of the free acid' in the fluid, which attacks the calcareous por- 

 tions and causes them to lose form or brilliancy, or both. 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. With formalin, as 

 with other preservatives, only one, or at any rate only a very few, 

 objects should be put into the same receptacle at the same time, and 

 there must be a good amount of fluid in proportion to the animal mat 

 ter present. For gelatinous animals the solution should be of !■ to 4 

 per cent strength. Carmarina and similar things may be killed and 

 hardened at the same time by the use of formalin of the right strength 

 and chromic acid of 1 per cent in equal parts. For animals of some 

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

 formalin solution, the general rule being that the softer the animal 

 the weaker the formalin. Either fresh or salt water may be used in 

 making the solutions, as may be convenient. The sea water solution, 

 indeed, preserves the transparency of gelatinous bodies better than the 



' It is said by the advocates of the tise of formalin that this free acid may he 

 neutralized by sodium carbonate and many of the objections to the fluid thus 

 removed. E. 0. H. 



