202 robert h. wolcott: 



the accumulation of individuals in vials prevented the correc- 

 tion of the recorded notes. These, together with a lack of that 

 familiarity with the Unionidse necessary to make sure identifi- 

 cations at the time of examination and consequent occasional 

 confusion in the recording of observations, impair the value of 

 early notes and collections. The facts are mentioned that 

 others may be warned thereby, and in order that certain allusions 

 in the descriptions which follow may be understood. It may 

 be said here, that in the case of more recent collections, care 

 has been taken to keep the mites from each mussel separate 

 until careful examination under the microscope, of the structure 

 of palpi, legs, genital area, etc., has allowed of exact identifi- 

 cation of each individual mite. 



As to preserving fluids, alcohol, corrosive sublimate, picro- 

 sulphuric, Flemming's and other solutions were at first used. 

 Of these corrosive sublimate gave the best results, but all have 

 been rejected as making the specimens too brittle and leading 

 to serious breakage of appendages. Formol does not preserve 

 the color effectually and is partly open to the same objections. 

 Yet a certain proportion of the specimens collected have always 

 been preserved in either it or the media previously mentioned, 

 to allow of their being studied in various ways. A solution 

 recommended by Koenike (91c) and consisting of 



Glycerine 2 parts by vol. , 



Distilled water 3 parts by vol. , 



Glacial acetic acid 2 parts by vol., 



Absolute alcohol 1 part by vol., 



has been found to preserve the specimens in the best condition 

 for future study, since although it cannot be recommended as a 

 preservative either of form or color, it keeps the body soft and 

 the appendages pliable, and thus they lend themselves the more 

 readily to methods of preparation used in making slide mounts. 

 A solution consisting of 



Glycerine 10 parts by weight, 



Citric acid, concentrated solution, 3 parts by weight, 



Distilled water 10 parts by weight, 



to which is added, when the mites have regained their plump 



