168 THE MICROSCOPE: ITS CONSTRUCTION, ETC. 



end. The tube B is terminated at its lower extremity by a dia- 

 phragm. In using this instrument i5 Ms pushed right down into 

 B, and the tubes, B and C are drawn out as far as possible from 

 the exterior tube A^ and the instrument is directed towards the 



I Oijeotzf. 



J 



OcuJ&L 



^ . bs > 



; 



Fig. 32. — Janssen's Microscope. 



object. In the foregoing notes we believe we have taken a fair 

 survey of the book, and in doing so have selected such of the illus- 

 trations, kindly lent to us by Mr. Baxter, as we thought would be 

 most interesting to our readers. The article on the Future of the 

 Microscope is comprised in a long letter by Dr. S. Czapski, and 

 will be found towards the end of the volume ; this we will leave 

 our readers to peruse at leisure from the volume itself. There is a 

 full and comprehensive Glossary-Index. 



Staining Jneect ZTiaeuee* 



AT a meeting of the Entomological Club of the American 

 Association for the Advancement of Science, 1891, Mr. 

 Smith made a few remarks on Staining Insect Tissues. 

 He had found considerable trouble in his studies on differentiating 

 parts, and especially those structures that tend to become trans- 

 parent. After considerable experimentation he had found nigrosm 

 one of the most satisfactory stains for trachea and glands, and 

 many of the membranaceous structures. It does not touch 

 chitine. By the use of this stain he had followed the trachea to 

 the tips of the antennae and into the labella of flies. Saffronin is 

 another valuable stain, and especially for chitinous structures, for 

 which it seemed to have a special affinity. Combining nigrosin 

 and saffronin often gives very pretty results. Care should be 

 exercised not to leave the objects in saffronin too long, as it is apt 

 to result in a uniform and too intense colour, which is hard to get 

 rid of. Hsematoxylin gave very poor results, and he does not look 

 on it with favour. Eosin is excellent where only a slight stain is 

 desired, and has given some beautiful results. The use of such 

 methods in studies admitting of them will solve many problems 

 that are still obscure. — Canadian E?ttomologist. 



