XVIII, 4. Foot a. Strobell: Amethodoffocussing in photomicrography. 421 



Befriedigung angefertigt und kann von ihm um den Preis von 170 Mk. 

 bezogen werden. 



'&' 



[Eingegangen am 4. Februar 1902.] 



A new metliod of focussiiig in photomicrography. 



By 

 Katharine Foot and Ella Ghurch Strobell, 



Woods Hole, Mass, ü. S. A. 



With platelll and one woodcut. 



If photomicrography is to be of practical value to cytologists, 

 a simplification of the present methods is needed, in order to place 

 it witbin reach of investigators not baving access to the complicated 

 and expensive outfit now considered indispensable for the work. And 

 to be of real Utility, photography should compete favorably in points 

 of convenience with drawings by pen and pencil. The present me- 

 thods certainly do not offer these advantages — with the highly 

 specialized apparatus demanding an arc light, setting apart of a 

 separate roorn, and in many cases, a special Operator to conduct 

 the work. 



Several years of experience in pbotographing the egg of Allo- 

 lobophora, has convinced us of this need, and it has been our aim 

 to simplify the process without sacrificing the Standard of work. 

 This we have done by substituting a new method of focussing and 

 we hope in the present paper to illustrate its practical value. Apart 

 from the accuracy and ease with which it enables the cytologist to 

 reproduce the most minute details in the cell , it does away with 

 the necessity of a complicated and expensive camera. Given the 

 equipment which is to-day within the reach of every microscopist — 

 a microscope with the best apochromatic lenses, — the additional 

 outfit required for photography need be no more expensive than the 

 best camera lucida. 



