THE 



MONTHLY MICROSCOPICAL JOURNAL. 



JUNE 1, 1871. 



I. — Additional Observations concerning the Podura Scale. 

 By Dr. J. J. Woodward, U. S. Army. 



(Read hsfore the Royal Microscopical Society, May 3, 1871.) 



February 7th, 1871, I had the honour to forward to the Eoyal 

 Microscopical Society a paper " On the Structure of the Podura 

 Scale, and certain other Test-objects, and of their representation by 

 Photo-micrography." This paper was accompanied by a number of 

 photo-micrographs, one of which (No. X.) was not as satisfactory, in 

 the paper prints, as I could have wished. Subsequent experience 

 has increased my confidence in the opinions expressed in that paper 

 with regard to the scales of the test Podura {Lepidoc^jrtus curvi- 

 collis), and a fortunate circumstance has given me the opportunity 

 of representing these views in a more convincing manner. 



Shortly after my paper had been forwarded, I received a visit 

 from Mr. Joseph Beck, who is spending a few months in the United 

 States. Mr. Beck had with him an excellent microscope, the work- 

 manship of the well-known firm of which he is a member, and a 

 number of fine high-power objectives by the same house. With 

 these objectives he exhibited to me several slides of the scales of the 

 Lejndocyrfus curvicollis, collected by himself from carefully-identi- 

 fied insects. He aimed at the exhibition of the exclamation marks 

 as such, using a right-angled prism, achromatic condenser, and 

 small coal-oil lamp. Before leaving Washington he was so good as 

 to give me one of these slides, indicating on it a scale which appeared 

 particularly adapted to the display of the exclamation marks. 



Certainly this scale, which was y^crth of an inch in length, and 

 yrffth of an inch broad at its widest portion, surpassed in the dis- 

 tinctness of its markings any of the scales of this species which have 

 hitherto come into my possession. With central monochromatic 

 Hght, the immersion Tr.th, and amphfier, I obtained a negative 

 showing the exclamation marks better than any representation of 

 the kind I have yet been able to obtain. I send herewith a paper 

 print. The magnifying power is 3200 diameters. 



But immediately afterwards, with the same optical combination 



VOL. V. X 



