1893.] MICROSCOPICAL JOtKNAL. 61 



5. Light for Photographing. — I wish to photograph a 

 honey-bee that is mounted on a i|^-in. slide. With 3-inch B. & L. 

 student's objective I get too large magnification and too small a 

 circle of light. It is about 3 inches only, and I want to use a 

 4 plate. I cannot get a 4-inch objective to give any more light. 

 — Student. 



6. Hardening Balsam and Damar. — I have trouble with 

 balsam and benzole, also with damar in benzole, on account of 

 its hardening slowly. Several lots from difterent makes give 

 same results. Can mild heat be used, or is there some better 

 medium for quick work, reliable and easy of manipulation? 

 — Amateur. 



7. Nervous System of Sponges. — Referring to the note on 

 page 4S regarding the nervous system of the fresh-water sponges, 

 request is made for the titles of any or all papers that have been 

 published on the subject. — The Editor, in behalf of J. M. S. 



S. Farrant's Medium. — Why do dealers charge 50 cents for 

 an ounce of Farrant's medium, or why does any one buy it of 

 them, when anybody can make it for himself at less than 3 cents 

 per ounce f 



Picked lumps gum acacia, . . 4 drams. 



Glycerin, ..... 2 fluid drams. 



Camphor water, . . . . 4 " " 



Mix, let it dissolve, and strain. — F. 



LETTERS TO THE EDITOR. 



Note. — TA/s column is open to all correspondeiits zu/io 7V)ile upon the 

 topics enumerated under " Problems" or ■who give other information of 

 interest. The fact that a problem has been anstvertd once need not deter our 

 friends from making additional comtnents. To facilitate reference, corre- 

 spondents should cite the number as well as the page on ivhich have ap- 

 peared letters and queries to -which rcferejice is made. The editor is not 

 responsible for the views 0/ others published in this periodical. 



(5) Societies. — We are endeavoring to compile as correct a list 

 as possible of existing microscopical societies in the U. S. I 

 have written to all that I have ever heard of, but suspect that there 

 are many others. As your journal goes everywhere, will you not 

 request that the secretaries of all such societies communicate with 

 me, giving name and location of society, date of organization and 

 incorporation, names and addresses of officers, number of mem- 

 bers, time of meeting, publications, library, cabinet, etc. .'' — George 

 Otis Mitchell, 1034 Pine street, San Francisco, Cal. 



(6) Methods of Instruction. — You and your readers may be 

 glad to learn that an experiment in medical education with the 



