178 The Microscope. 



GLEANINGS FROM OUR FOREIGN EXCHANGES. 



C. H. STOWELL. 



BEADS OF AMPHIPLEURA. Speaking of the photographs 

 of this diatom made by Dr. Van Heurck, and of the discus- 

 sion arising from the beaded appearance shown bj r the photo- 

 graph, this journal says : " Thus in the case of the ' beads ' of A 

 pellucida the existence of such an image proves that the diatom 

 has not merely a periodic differentiation of structure in one di- 

 rection, but that such differentiation exists in two directions 

 which cross at right angles." It says further that what the 

 diffraction theory shows is that the real form and structure of 

 the beads cannot be determined by the mere inspection through 

 the microscope of their images. The microscope leaves unde- 

 cided questions of elevation, depression, centres of thickening, 

 etc. 



Preparation of Spider. The spinneret, leg and falces 

 having been removed from the spider are placed separately 

 in liq. pot. for 24-36 hours ; wash in water; place in acetic acid; 

 soak in water; place in alcohol for short time; clear in oil of 

 cloves; transfer to turpentine; mount "without pressure in cells." 

 The tongue of the spider, carefully dissected out, makes a beau- 

 tiful preparation. The eyes may be mounted in balsam, in cells, 

 as opaque objects, with fine results. 



Nothing New. Mr. Crisp exhibited a microscope before 

 the Royal Society made in 1686,, which had a spring used 

 for adjusting the focus of the lens, which spring "was the sub- 

 ject of a patent about fifteen years ago." 



Sections of Hard Organized Substances. The object (a 

 piece of hard wood, for instance,) is first filed level with 

 an ordinary file and made more even with finer files. A 

 piece is now cut off from that portion which has been filed 

 smooth. The filed surface of this piece is now fastened to a slide 

 with a drop of Canada balsam. Of course the object is pressed 

 firmly to the slide, and the warm balsam allowed to get cold 

 and hard. Then the section is filed until it is smooth and shin- 

 ing and transparent enough. After the final filing and polishing 

 the section is cleaned with a cloth wet in alcohol, a drop of bal- 



