372 KANSAS UNIVERSITY SCIENCE BULLETIN. 



rough bibulous paper until the envelope is left behind ; if care- 

 fully done, the eggs quickly roll out onto the paper uninjured. 

 They can then be placed directly in strong alcohol, prefer- 

 ably 98 per cent. This is better than using successive grades 

 of alcohol, as it saves time, reduces the dangers of handling and 

 causes no appreciable distortion. The eggs are then cleared in 

 creosote or turpentine and are ready to mount. These oils are 

 preferable to xylol as they leave the material less friable. A 

 few drops of thick balsam are placed on a slide, and one or 

 more eggs, after being rinsed with xylol, are laid on this and 

 allowed to sink into it. The balsam should be thick enough 

 to form a mass of sufficient depth entirely to submerge the 

 eggs, as, otherwise, if any of the gelatinous matrix is left upon 

 them, it takes up minute air-bubbles as drying proceeds. If 

 Care has been taken to select only eggs that orient themselves 

 satisfactorily in the preserving fluid, this same orientation will 

 be maintained in the balsam mount. This is rather an impor- 

 tant precaution, as, without it, the eggs are likely, before the 

 mount is dry, to take an unsatisfactory position that can not 

 well be remedied. The eggs may be mounted either singly or 

 in a series with about equal ease. 



After the balsam has hardened enough to hold the eggs 

 firmly in situ — one or two days — a protecting cover is placed 

 upon them. An ordinary cover-glass, supported on bits of 

 glass, can be used by putting it in place and filling in with 

 balsam from one side. A little xylol should be run over the 

 balsam just before the cover-glass is put in place, to avoid 

 getting air-bubbles into the mount. Rather a more satisfactory 

 covering, however, is a small watch-crystal, 10 or 15 mm. in 

 diameter, the size depending upon the number of eggs on the 

 slide. A drop of xylol is put into the crystal, which is then 

 filled rounding full of thick balsam. Another drop or two of 

 xylol is poured over it and any air-bubbles present removed. 

 Then the slide holding the eggs in their balsam matrix is 

 similarly moistened with xylol and inverted onto the watch- 

 crystal so as to enclose the eggs. The convexity of the matrix 

 does away with the chief difficulty of watch-crystal mounts — 

 the tendency of the fluid to run out sidewise, thus introducing 

 air. The mount is now ready to set aside to harden; care 

 must be taken, however, that a good ring of balsam entirely 

 surrounds the edge of the crystal so that air cannot be drawn 

 in as the balsam dries. 



