380 THE AMERICAN MONTHLY [Nov. 



the sections cut by an assistant or by different members 

 of the class at different times. A description of a con- 

 venient freezing device and methods of imbedding in 

 aqueous media will be published by one of us in the next 

 number of this journal. 



Freezing methods and the preservation of natural 

 form and size of the different parts with as little change as 

 possible have rendered it very desirable that aqueous 

 media be employed if possible for preserving fluids, 



A number of fluids have been subject to experiment by 

 the writers for about three years, particularly upon the 

 abundant materials of all groups of algge obtained at 

 the Marine Biological Laboratory at Woods Holl, Mass. 

 It is thought by the writers that these notes of their ex~ 

 perience, while containing nothing especially new, may 

 serve as useful hints to those who have before them the 

 problem of providing and preserving cryptogams for 

 laboratory purposes. 



Chrome alum. — This substance was used by Guignard 

 for fixing various Laminariacea; for the purpose of inves- 

 tigating the structure and development of the mucilage 

 ducts. Later it has been tested at the Biological Station 

 at Helgoland by Lotsy upon the red alg^ particularly 

 as to the preservation of the cell-structure. 



The writers have used one per cent chorme alum in 

 either distillpd water or sea water carefully filtered 

 through sand, according to the different habitat, for 

 about four years. The algas, carefully selected and 

 washed free from dirt and debris, have been placed in it 

 at once and preserved in it until needed for examination. 

 The cell structure is well preserved in all cases. Very 

 little washing is needed afterwards to allow staining by 

 any of the ordinary staining reagents. Gelatinous inter- 

 cellular substances, whether soft or more cartilaginous, 

 are rendered firm but not especially opaque by treatment 

 with it. Cyanophycese, Chlorophycea3, and Rhodophy- 



