ZOOLOGY AND BOTANY^ MICBOSCOPY, ETC. 353 



own preparations made with pure balsam, I attributed tbem to the 

 chloroform. 



Shortly after I began using tolu a correspondent informed me that 

 some of his slides were spoilt by a kind of crystallization, which he 

 described as being like a delicate cobweb. I have noticed a similar 

 appearance in balsamed slides that had been overheated, and in con- 

 sequence the balsam had become brittle. I have sometimes seen the 

 formation of it when cleaning off the superfluous balsam ; a sudden 

 change of temperature, such as the heat of the hand, will produce it. 

 The appearance is caused by innumerable fissures permeating the film 

 of balsam. Tolu if hardened too much will no doubt act in the same 

 manner. Being of slightly higher refractive index than styrax, it is 

 useful for many forms, and I hope that this defect may be remedied 

 either by the use of benzole or by making the tolu less hard." 



M. J. Amann also,* as the result of nearly three years' experience, 

 considers tolu superior to Canada balsam and equivalent to styrax. 

 The only dravpback is that it has a little more colour than the latter, 

 though, like styrax, it becomes coloxirless with age and when exposed 

 to the light. On the other hand, it is much simpler to prepare. It 

 is only necessary to dissolve 1 part of the balsam in 2 or 3 parts of 

 chloroform, then filter, and it is ready for use. 



Mr. C. Van Brunt, however,f confirming a statement of Mr, E. G. 

 Day, speaks to the crystallization of balsam of tolu, even in sKdes 

 prepared by an experienced hand. 



Glycerin and Balsam Mounts. J — J. S. Kingsley, referring to the 

 praise recently given to glycerin as a mounting medium, considers 

 that for every-day work it cannot compare with balsam, and that the 

 difficulties connected with the use of balsam have been over-stated. 

 He gives the following comparative statements, the first being the 

 steps required with balsam, and the second with glycerin. 



a. Harden with chromic acid. h. Dehydrate with alcohol of 

 different grades, c. Transfer to chloroform, d. Transfer to paraffin. 

 e. Cut sections. /. Dissolve paraffin with turpentine, g. Place on 

 slide in balsam and apply cover. 



With glycerin we follow the same steps to /, and then we have to 

 add the following : — 



g. Get rid of turpentine by alcohol, h. Place on slide with 

 glycerin, and apply cover, i. Fasten cover. 



It seems to him "that some people needlessly take many steps in 

 doing microscopic work which are absolutely needless. For instance, 

 in the time one occupies in finishing a balsam slide he could mount 

 another, and in the experience of the writer all use of cements for 

 fastening the cover in the case of balsam mounts is unnecessary." 



Mounting in Phosphorus. § — E. Hitchcock referring to the re- 

 commendation to use Walton's glucine or Eay's coaguline as cements, 



* Bull. Soc. Belg. Micr., xi. (1885) p. 127. 

 t Journ. New York Micr. Soc, i. (1885) pp. 41-2. 

 t Science Eecord, ii. (1884) pp. 269-70. 

 § Amer. Mon. Micr. Journ., vi. (1885) p. 7. 

 Ser. 2.— Vol. V. 2 A 



