1892.] MICROSCOPICAL JOUENAL. 221 



MICROSCOPICAL SOCIETIKS. 



San Francisco, Cal. — Wm. E. Loy, Sec'v. 



JJay ^, i8g2. — President Bieckenfeld presided, and during tiie 

 evening spoke of the hurried visit to this city of Dr. A. C. 

 Stokes, of Trenton, N. J. After the reading of the minutes and 

 the disposal of the routine business, George Otis Mitchell exhib- 

 ited a novel and inexpensive collecting apparatus he had lately 

 constructed, vv"ith slight modifications from those heretofore used. 

 It consists of two wired tin rings, the outer slipping over the 

 inner and securing the net of bolting cloth. The net narrows 

 downward, the lower end lieing the size of a wide-mouthed two- 

 ounce bottle, around which it is listened with a piece of cord. 

 A socket fastened to the ring is of a size admitting the ferrule of 

 a walking-cane, which enables the collector to sweep through the 

 water at a considerable distance from the shore. Mr. Mitchell 

 thought a collecting apparatus of this kind would often secure 

 specimens of animal and vegetable life, when the most assiduous 

 work with the ordinary method would show nothing of interest, 

 or only such as are very numerous. With his apparatus he was 

 enabled to secure quantities of that most beautiful and elusive 

 fresh- water alga, Volvox globatoi% at any time he chose to take 

 a dip in Mountain Lake. 



The paper of the evening was read by R. H. Freund, on " The 

 Differential Staining of Cover-glass Preparations by Eosin." He 

 said aniline dyes were of two groups— the basic and the acid. 

 To the first belonged methyl-violet, gentian-violet, methyl-blue, 

 vesuvin, fuchsin, and a number of others. To the second group 

 belonged the derivates of the fluoresein group — eosin, methyl- 

 eosin, cocein, pyrosin, and aurantia. Koch and Weigert have 

 used the selective affinity of the basic colors for staining and dif- 

 ferentiating bacteria, and, taking Koch's researches as the base, 

 Ehrlich has succeeded in utilizing them in staining and differen- 

 tiating the cellular elements of the blood. He gave his method 

 the name of the Tinctorial or Color Analysis, asserting that cer- 

 tain dyes under all conditions produced invariably the same effect 

 on some cell elements, with the certainty of a chemical experi- 

 ment ; in fact he claimed that the result obtained was a chemical 

 compound formed between the dye and the object brought in con- 

 tact with it. 



A number of years ago Waldeyer (^Archivfilr Mikroscopische 

 Anaiomie J^I) observed that on different places on the loose 

 connective tissue are to be found large, round, coarsely-granular 

 cells, which he called embryonal or plasma cells. He asserted 

 that these cells had a disposition to absorb fat, and that in time 

 they might degenerate into fat cells. Investigating Waldeyer's 

 observations, Ehrlich found that these cells have a disposition to 

 absorb and retain certain aniline colors ; and following up his ex- 



