962 FRESH-WATER BIOLOGY 



desired to keep the shells as specimens, as it destroys those left in 

 it any length of time. 



With the exception of the larger species of Planorbis, which are 

 more easily cleaned by boiling, it is practically immaterial whether 

 the fluviatile univalves are boiled, or put directly into diluted alco- 

 hol for a day or two. In either case there is no difficulty in ex- 

 tracting the animals. The curved points of the collecting forceps 

 are convenient for this purpose, and hooks of various sizes can be 

 made from safety pins. By tying these on small wooden handles 

 very effective instruments can be made. Small hooks or "probes" 

 of various sizes fitting into an adjustable handle are most convenient 

 and can be obtained from any dealer in dental instruments. A 

 small, fine-pointed dental syringe is indispensable for this work. 

 When the animal is completely extracted, the interior of the shell 

 should be thoroughly washed out with the syringe. A small piece 

 of sponge on the end of a fine copper wire, which can be bent in any 

 direction, is very useful for removing the mucus, which is apt to 

 adhere to the interior. This should always be carefully attended 

 to; if not it will greatly disfigure the specimen when dried. The 

 exterior should then be thoroughly scrubbed with a soft tooth or 

 nail brush. When perfectly clean, inside and out, the water should 

 be carefully emptied out and the shell put aside in the air, but not 

 in the sun, to dry. 



It is not desirable to attempt to clean the minute species by 

 removing the animal. They should be put directly into 25 per cent 

 alcohol for a day or two. If to be left longer in the alcohol, the 

 strength should be increased. Twenty-four hours, however, in the 

 alcohol is all that is necessary. Then they can be dried in the air 

 without leaving any offensive odor. Either before or after drying 

 they can be cleaned, if necessary, by putting them in a bottle of 

 water, with some fine, clean sand, and shaking them together until 

 all the dirt has been removed by the sand. In the operculate 

 species, it is desirable to retain the opercula of, at least, part of the 

 specimens. While it adds to the labor, it increases the value of 

 the specimen if it is always done. These are easily removed from 

 the animal and, after being cleaned, should be put inside the shell 

 and the aperture plugged with cotton. All the foreign matter both 



