TWENTY-THIBD ANNUAL MEETING. 83 



should be taken that the water nsed for washing is chemically pare, or else crystals 

 will be formed, attaching the diatoms to each other or to the slide. Moreover, if all 

 the acid has not been washed out, crystals will likewise be formed. As an instru- 

 ment for picking up the diatoms, a sharpened swine's bristle or a mouse's whisker will 

 be found most excellent. If the experimenter wishes to mount them free hand 

 under the microscope, this bristle may be fastened to a pen-holder or any handle 

 by means of a drop of wax or Canada balsam. Since a diatom xt^Vo of an inch long 

 is considered above the average size, and few of the varieties found about here are 

 of the larger varieties, one finds free-hand mounting almost an impossibility. I 

 experimented for three months last spring, and was rewarded by a loss of patience 

 and enthusiasm, but succeeded in acquiring a steady hand, and alas! but five mounts. 

 By using the mechanical finger, however, I have succeeded within the last month, 

 working at odd moments, in selecting out and mounting about fifty varieties. All 

 these varieties have been selected from collections made from one stream. I usually 

 select out eight or ten of a variety and transfer them to a cover-glass lightly coated 

 with glycerine. The glycerine is evaporated by the heat of an alcohol lamp, leaving 

 the diatoms firmly attached to the cover-glass. A drop of Canada balsam is placed 

 upon a slide, and the cover-glass is gently dropped upon the balsam. The slide is 

 kept for several days with the cover-glass side downward until the balsam is sufii- 

 ciently hardened to prevent any change of position taking place. 



I might venture to add that, like other plants, certain varieties of diatoms seem 

 to flourish at different seasons of the year. Perhaps my observations are too limited 

 to allow me to make, with any definiteness, such a statement. From the same ra- 

 vine, however, I made collections last February and May. The varieties that pre- 

 vailed in February were fewer in May. Collections made from the same place in 

 September of this year show that varieties seldom seen in the spring — for example, 

 Pleurasigma, Navicula, and some of the Surirella, as robusta, are plentiful. While 

 some varieties so common in the spring, as Surirella spiralis, I have failed to find at 

 all this fall. Whether these varieties "run out," so to speak, and regenerate more 

 frequently than once a year, that is, at more than one season of the year, I cannot 

 of course determine from but one year of observation. It is evident that they have 

 resting seasons. I might add, however, that some varieties, as Synedra, seem to be 

 uniformly distributed throughout the seasons. 



A COMPARISON OF PRESERVATIVE FLUIDS FOR MUSEUM USE. 



BY V. L. KELLOGG AND E. E. SLOSSON, LAWKENOE. 

 [Abstract.] 



A satisfactory preservative fluid for museum use, especially for the preservation 

 of insect forms, is a desideratum of much importance. Much trouble and lack of 

 success is experienced in the endeavor to preserve specimens without shrinkage, or 

 swelling, or loss of color. A satisfactory preservative fluid for biological collections 

 in entomology must perfectly, or as nearly perfectly as possible, preserve the animal 

 tissue from deterioration, and must not change the colors. Alcohol is the most com- 

 monly-used preservative fluid, but while preserving the tissues, it affects colors in 

 almost all cases. Specimens kept in glycerine frequently retain their colors, but 

 are likely to fall to pieces on being handled. Carbolic acid effects marked changes 

 in the tissues. 



The experimenters have prepared an extensive series of preservative fluids, so- 



