62 THE AMERICAN MONTHLY [Fab 



Dr. Hebb said Prof. Groves had made some modification 

 in a form of hand-microtome, and had sent it for exhibi- 

 tion. The President called attention to six photomicro- 

 graphs of the larvae of gnats, taken from life, by Mr. J. T. 

 Holder. The President exhibited an old Gillett condenser, 

 dated July 20, 1849, which had a collar adjustment. Dr. H. 

 C. Sorby's paper, "On the Preparation of Marine Worms 

 as Microscopical Objects," was read. The subject was 

 illustrated by beautifully-mounted slides exhibited under 

 microscopes. The attention of the meeting- was then di- 

 rected to a fine exhibition of Foraminifera, by Mr. Ear- 

 land, shown under a large number of microscopes, with 

 descriptions explaining the points of interest in each slide. 



MICROSCOPICAL MANIPULATION. 



Mosses. — Every bryological student should cultivate the 

 habit of preserving microscopic mounts of the character- 

 istic portions of the mosses which have been studied. A 

 collection of this sort is an invaluable adjunct to the her- 

 barium, and these mounts are constantly being referred to 

 in subsequent studiesof the same or nearly related species. 

 A mica mount has a great advantage over the glass for 

 this purpose, as it can be kept in a small envelope fastened 

 to the herbarium sheet with the dried plant, and is thus all 

 ways easily consulted and can readily be sent through the 

 mail. The mica slide should be fairly stiff and about two 

 inches by seven-eighths of an inch. The mica cover should 

 be thinner than the slide and of generous proportions, as 

 compared with the ordinary glass cover. Glycerine-jelly is 

 generally used as the mounting medium, and the method of 

 procedure is essentially the same as in making glass mi- 

 croscopic mounts. 



It is seldom necessary to use an extremely high power 

 objective in studying the mosses, so that the objection off- 

 ered by some raicroscopists to the use of mica slides (viz., 

 that modern objectives have been adapted to a certain 

 thickness of cover glass and any change in that thickness 

 or substance affects the image) is seldom if ever realized. 



