2(36 THE AMERICAN MONTHLY [Sep 



tive glow-light is produced between it and the wood. It 

 this proposed to try this meod for copying drawings and 

 for other purposes. 



Diatoms. — In collecting, a spoon attached to a stick 

 may be used for skimming the brown diatomaceous ooze 

 off the surface of the mud ; a drag net serves this purpose 

 in the case of forms occurring at greater depths, e. g., 

 Surrirella. The latter should be placed with water in shal- 

 low glass vessels sheltered from direct sunlight. The dia- 

 toms will appear in masses on the surface of the mud af- 

 ter twelve hoars. Transfer them by means of a pipette 

 to the fixing fluid. Fleming's chromo-aceto-osmic acid, 

 and sublimate, in aqueous or alcoholic solution, is recom- 

 mended as being the best reagent for demonstrating the 

 delicate structural features of the nucleus and cytoplasm 

 during division. The chromatic elements of the nucleus 

 are well shown by picro-sulphuric acid followed by haema- 

 toxylin. The arrangement of the cytoplasm, the chro- 

 matophores, and other inclusions in the cell may be well 

 brought out, in unstained preparations, by a one percent 

 osmic acid solution. A solution of iodic alcohol (45 per 

 cent) is recommended for the study of the so-called "red 

 granules" of Butschli, which, by the foregoing method, 

 stain well after fixing. Large forms receive a somewhat 

 different treatment. They are removed individually with 

 the aid of a capillary tube and a dissecting microscope, 

 and are transferred to the fixing bath. The solution is 

 decanted off after fifteen minutes and the objects are pass- 

 ed through water and alcohol, of strengths increasing to 

 the absolute point. This extracts oil and the coloring 

 matter of the chromatophores. The preparation is then 

 passed through alcohols of decreasing strength into dis- 

 tilled water, after which it is stained in a weak solution 

 of Delafield's haematoxylin. The material is then passed 

 successively through 35, TO, 95 per cent and absolute alco- 

 hol into clove oil and finally mounted in dammar. 



