Thk Microscope. 12! 



and colifined in broad encircling bands. Also tor slides of 

 trachea- from a beetle, the larva of the hickory borer, etc. — 

 To Dr J. Edw. Line, Rochester. N.Y., for photo-micrographs 

 of living Tubifex. — To Dr Wm. N. Beggs for sections of testis 

 and of lung of chicken and a section of human kidney. These 

 are all well cut and mounted, but the section of kidney is one of 

 the best and most instructive preparations of the kind that I 

 have ever seen. The epithelial cells within the uriniferous 

 tubules with their large nuclei are beautifully displayed, but the 

 capillaries forming the glomeruli are emphatically conspicuous 

 and are naturally injected with their own blood, the corpuscles 

 still remaining in situ. The same may be said of many of the 

 transverse and even of some longitudinal sections of the larger 

 blood vessels. The preparation has been skillfully made and is 

 exceedingly instructive. Also for a section of rat's liver showing 

 the very rare formation of tyrosine crystals. This is in lustrous, . 

 needle-like crystals, in many instances collected in clusters and 

 radiating masses. Aside from the beauty of the crystals, the 

 slide possesses .more than ordinary interest as a pathological' 

 specimen. 



THE WORKERS 



Si'HLCTUKE OF THE DIATOM VALVE. — Two remarkable })apers on 

 this subject, one by Mr T. F. Smith, the other by tlie Hon J. D. 

 Cox, appear in the April numb^ of the Journal of the New York 

 Microscopical Society. The following is a resume of these essays. 



Mr Smith's paper opens by correcting some of the conclusions 

 he had made public in reference to the structure of the Diatom 

 valve in a former paper of his read before the Quekett Club in Sep- 

 tember 1888. He thinks that the use of the apochromatic lenses 

 with the illumination of a very wide cone of light from the 

 achromatic condenser enables him to reveal by photography the 

 following new points in the structure of Pleurosigma formosum : 



1. The shell has three layers which may l)e discriminated by 



