42 



THE AMERICAN MONTHLY 



[March, 



Sections so stained, and mounted 

 in balsam, will be found to possess 

 all the differentiation given by hema- 

 toxylin, with a change from the pur- 

 plish blue color to the subdued tones 

 of brown — a substitution often most 

 pleasing and grateful to the eye. 



While in general appearance these 

 sections resemble successful Bismarck 

 brown staining, there are differences 

 in color, the modified hematoxylin 

 possessing a peculiar grayish brown 

 tint, in addition, the differentiation 

 being better marked, and much more 

 readily obtained than with the Bis- 

 marck brown, which is sometimes 

 rebellious. 



For photography, these modified 

 stain ings are well adapted, since the 

 thinnest possible layers are sufficiently 

 non-actinicto yield a vigoi'ous picture. 

 A comparison of the results obtained 

 from delicate sections stained with 

 carmine or hematoxylin, as usually 

 employed, and ones colored as sug- 

 gested, will convince that in the mod- 

 ified hematoxylin we possess a really 

 useful and very convenient method of 

 preparing tissues for photography. 

 o 



Beadini:: of Amphipleura and 

 Photo-Micrography. 



BY THE EDITOR. 



Dr. Henri Van Heurck, who has 

 been investigating the structure of the 

 frustules of Amphipleura pellucida 

 with great care, with the best objec- 

 tives, has favored us with a photo- 

 graph showing a portion of a valve 

 resolved into dots. It was made with 

 a yig-inch homogeneous objective of 

 Zeiss ; the illumination was with an 

 incandescent electric lamp and verti- 

 cal illuminator ; amplification 3,000 

 diameters. 



The print shows what may be 

 called a beaded structure clearly 

 enough, although as a whole the 

 picture lacks the sharp definition 

 which is seen in the excellent prints 

 made by Dr. Woodward. This, 

 however, is probably a natural con- 

 sequence of the method of illumina- 



tion employed. The median line 

 seems not to be in focus, and the 

 margin of the valve on one side — the 

 side on which the markings are seen 

 — is very irregular and ill-defined. 

 The portion of the valve on the other 

 side of the median line is almost 

 wholly lost. A small portion only, 

 probably what was in the middle of 

 the field of view, shows the mark- 

 ings. 



It can scarcely be expected that a 

 photograph of such a difficult object — 

 so extremely difficult to resolve that 

 the markings have escaped the closest 

 scrutiny of many competent observers 

 who have sought to find them — 

 should be sharp and entirely satisfac- 

 tory. The appearance actually pre- 

 sented is of a series of longitudinal 

 lines crossed at right angles by trans- 

 verse lines. Closer examination shows 

 an approach to a dotted structure, such 

 as one observes in other diatoms with 

 coarser markings just before they are 

 perfectly resolved into dots. The 

 two systems of lines are clearly seen, 

 however, and the only question that 

 can now be raised against the conclu- 

 sions of Dr. Van Heurck, is whether 

 the structure represented in the photo- 

 graph is real, or a result of diftraction 

 caused by the particular method o 

 illumination. This question can only 

 be answered by actual work with the 

 microscope, and even then it may not 

 be easily decided. 



Accompanying the photograph was 

 a letter from Dr. Van Heurck, which 

 we have translated and now publish 

 below. It contains information con- 

 cerning photographic work with the 

 microscope that is of great interest. 



Dr. Van Heurck writes as follows : 



' The print I send you was made 

 from a preparation of silvered diatoms 

 similar to those which Dr. Moore sent 

 to the Royal Microscopical Society 

 of London. I do not know what 

 process Dr. Moore employed, but 

 my method of silvering is simple and 

 easy. It gives perfect results and al- 

 ways the same. I give the process 

 in the "Synopsis of Diatoms." I 



