88 POPULAR SCIENCE MONTHLY. 



cated. A mixture of formalin and alcohol is favorable to the pre- 

 servation of markings. In the museum all specimens should be 

 removed at once from formalin to alcohol. No substitute for alcohol as 

 a permanent preservative has been found. The spirits derived from 

 wine, grain, or sugar is much preferable to the poisonous methyl or 

 wood-alcohol. 



In placing specimens directly in alcohol, care should be taken not to 

 crowd them too much. The fish yields water which dilutes the spirit. 

 For the same reason, spirits too dilute are ineffective. On the other 

 hand, delicates fishes put into very strong alcohol are likely to shrivel, 

 a condition which may prevent an accurate study of their fins or other 

 structures. It is usually necessary to change a fish from the first alcohol 

 used as a bath into stronger alcohol in the course of a few days, 

 the time depending on the closeness with which fishes are packed. In 

 the tropics, fishes in alcohol often require attention within a few hours. 

 In formalin, there is much less difficulty with tropical fishes. 



Fishes intended for skeletons should never be placed in formalin. 

 A softening of the bones which prevents future exact studies of the 

 bones is sure to take place. Generally alcohol or other spirits, arrack, 

 brandy, cognac, rum, sake, 'vino' can be tested with a match. If 

 sufficiently concentrated to be ignited, they can be safely used for pre- 

 servation of fishes. The best test is that of the hydrometer. Spirits for 

 permanent use should show on the hydrometer 40 to 60 above proof. 

 Decaying specimens show it by color and smell, and the collector 

 should be alive to their condition. One rotting fish may endanger 

 many others. With alcohol it is necessary to take especial pains to 

 ensure immediate saturation. Deep cuts should be made into the 

 muscles of large fishes as well as into the body cavity. Sometimes 

 a small distilling apparatus is useful to redistil impure or dilute 

 alcohol. The use of formalin avoids this necessity. Small fishes should 

 not be packed with large ones; small bottles are very desirable for 

 their preservation. All spinous or scaly fishes should be so wrapped 

 in cotton muslin as to prevent all friction. 



The methods of treating individual groups of fishes and of hand- 

 ling them under different climate and other conditions are matters to 

 be learned by experience. Eternal vigilance is the price of a good 

 collection as it is said to be of some other good things. Mechanical 

 collecting, picking up the thing got without effort and putting it in 

 alcohol without further thought, rarely serves any useful end in science. 

 The best collectors are usually the best naturalists. The collections 

 made by the men who are to study them and who are competent to do 

 so are the ones which most help the progress of ichthyology. The stu- 

 dent of a group of fishes misses half the collection teaches if he has 

 made no part of it himself. 



