Boyal Microscopical Society. 151 



Certain photographs of the Podura scale, made at the Army Medical 

 Museum, which induced him to publish at that time the results of 

 his previous, but still incomplete, studies. As these photographs 

 were all made with dry lenses, 1 took an early opportunity to re- 

 examine the scale with the immersion xVth of Powell and Lealand. 

 But although direct sunliglit reflected from a plain mirror gave 

 glimpses of a structure distantly resembling the new descriptions, 

 the resolution was so unsatisfactory that I was inclined to regard 

 the appearances as spurious, and more convinced than ever that the 

 scale was properly resolved when the exclamation marks were 

 shown. I made the two photographs sent with my note of 

 April 23, 1870, to Mr, Hogg.* Copies of these photographs accom- 

 pany the present paper. No. I. shows the notes of exclamation as 

 figured by Mr. Eichard Beck, in his work on the Microscope. In 

 No. II. there is a pretty distinct knob at the head of each note of 

 exclamation. Both photographs are magnified 3000 diameters by 

 Powell and Lealand's immersion -^^ih.. 



In my note to Mr. Hogg I expressed two wishes, both of which, 

 I am happy to state, have been gratified. The first was, that he 

 would obtain for me, from Dr. Pigott, one or two of the slides used 

 for his observations ; the second, that my friend Dr. Maddox might 

 be induced to photograph the Podura scale as seen by Dr. Pigott. 



In response to the first of these wishes, I received from Mr. 

 Hogg two slides ; one of the test Podura, the other labelled De- 

 geeria Nigro-maculata ; f the first from Dr. Pigott, the second from 

 Mr. S. J. Mclntire. To these gentlemen I desire to express my 

 sincere thanks. 



The response to my second wish was not less satisfactory. Dr. 

 Maddox undertook the photographic representation of both Degeeria 

 and test Podura, and has kindly sent me copies of the interesting 

 series of pictures exhibited by him to the Society last June.| 



Under these circumstances I renewed my observations, with the 

 intention of making a series of photo-micrographs representing such 

 appearances as I should be able to find. 



And here I desire to offer a few remarks with regard to the real 

 significance of photo-micrography, as a means of recording honestly, 

 and without modifications of subjective origin, the appearances 

 actually seen in the case of difficult test-objects. 



In his paper " On the Diatom Prism " § the late lamented Presi- 

 dent of the Koyal Microscopical Society, the Kev. J. B. Eeade, 



* ' Monthly Microscopical Journal,' vol. iii., p. 324. 



t Sir John Lubbock, in his " Notes on the Thysanura," ' Lin. Soc. Trans.,* 

 vol. xxvii., p. 277, names this scaled species of Degeeria, Seira domestica (^seh-a, a 

 chain), from the circumstances that it " forms a very interesting link (or chain) 

 between several genera, some of which aj^proach very closely to Lepidocyrtus," 

 &c. 



X 'Monthly Microscopical Journal,' vol. iv., pp. 51, 67. § lb., vol. ii., p. 5. 



M 2 



