356 SUMMARY OF CURRENT RESEARCHES RELATING TO 



"Working Session" of American Society of Microscopists. — 

 A leading feature of the last (Annual) meeting of this Society was 

 the " Working Session," an afternoon of the week of meeting being 

 devoted (under the direction of Mr. E. H. Griffith) to the practical 

 exhibition and explanation of methods of manipulation and investiga- 

 tion, with the view to improvement in technique. Three hours were 

 occupied, the first devoted to preparatory work, the second to finishing 

 work, and the third to questions and discussions. Four pages of the 

 ' Proceedings ' contain twenty practical questions which were asked, 

 with answers and suggestions.* 



Compound Eyes and Multiple Images.f — J. D. Hyatt finds that 

 to show multiple images in compound eyes it is best to cut out with 

 a small punch a circular disk not larger than can be pressed flat 

 without disturbing the facets. The most perfect eye for giving images 

 is that of the cockroach. It is very brittle, and so only a small part 

 of the cornea can be pressed flat in one piece. A piece large enough 

 to fill the field of a 1/2 in. objective and B eye-piece can, however, 

 be cut out, and the many advantages which it possesses more than 

 counterbalance its want of superficial extent. They can be mounted 

 in glycerin, and thus kept quite transparent without losing their 

 properties as lenses. 



The eye of a mosquito can be made to show 200 and more pictures 

 of a person in silhouette with great distinctness. The eye of Limulua 

 will also give multiple images, a small disk cut from the central part 

 being used. Also the minute globules of water produced by breathing 

 on a slide, and even the transparent parts of any structure which are 

 lenticular or globular. 



The fact of the image being erect or inverted may, it is suggested, 

 be of " service in determining the character of minute bodies or 

 structures, such as human blood-corpuscles, all of which show erect 

 images ; a proof that they are nucleated or at least lenticular at the 

 centre. The head of the pin-shaped sponge-spicule and the nuclei 

 in certain diatoms produce inverted images." 



Examination of Butter and Fats.|— T. Taylor (U. S. Depart- 

 ment of Agriculture) describes his observations on " artificial butter." 

 Formerly oleomargarine was easily detected, but latterly the manu- 

 facture has been so much improved as to make the task much more 

 difficult. 



In the early stages of investigation by the Microscope, it was 

 considered that butter might be distinguished from oleomargarine by 

 a comparison of the oil-globules of each ; but it was found that this 

 was an unreliable method. Aware of the fact that all artificial butter 

 was made directly from crystallized fats, he then devised a method by 

 which it could be distinguished by using Nicol prisms. Butter being 

 destitute of free fats, the colours of polarized light would not appear. 



• See Proo. Amer. Soc. Micr. 7th Ann. Meeting, 1884, pp. 199-219. 

 t Journ. New York Micr. Soc, 1. (1885) pp. 33-7. 



X Taylor, T., 'Microscopic Observations. Internal Parasites in domestic 

 Fowls and Butter and Fats.' 8vo, Washington, 1884, 7 pp. and 1 pi. 



