Boyal Microscopical Society. 25 1 



examination I do not know how many times ! However that may 

 be, — and I am sure I do not want to plagiarise — I can honestly 

 advocate the use of this "double illumination," in the examination 

 by " reflected " light of semi-diaphanous objects, which I take to com- 

 prise the majority of objects examined by the aid of the microscope. 



To proceed to the Battledore scales. I am glad to say that I 

 have found no reason to alter my opinion with respect to the tuber- 

 cular bodies I described in a former pajjer as existing on the surface ; 

 they were plainly enough seen in Ly. Alexis by reflected light, 

 but they could not be so readily made out in other species ; this 

 was unsatisfactory, as opposed to the usual harmony of the structure 

 which is found to obtain in allied species ; and moreover, as these 

 quasi tubercles were more easily seen under transmitted hght, it 

 was suggested to me by an acute and intelligent observer, that these 

 tubercles were really inside the scale, and formed part of a frame- 

 work, and so held up, or pushed up the inner membrane of the scale 

 in such a manner as to show on the surface as so many " lumps " 

 or " bumps." I confess that in my inability to see the tubercles on 

 the majority of the Battledores under reflected light, other than as 

 shadowy, slight elevations, I was inclined to think that this " frame- 

 work " view of the structure must be correct ; but then the rows of 

 distinct tubercles with stems and rounded heads on Ly. Alexis 

 were so very real, and on a foreign specimen kindly sent to me by 

 Mr. Mclntire were absolutely so " staring " by reflected light, that 

 I felt it necessary to re-examine more vigorously the whole series 

 of scales, and to modify if possible that exaggeration of light and 

 shadow which only dazzled and confused me. Hence the employ- 

 ment of the " double illumination " which I have described, and 

 which made it at once evident that there was really no want of har- 

 mony of structure, inasmuch as I was now able to make out, so soon 

 as the secondary light had removed the too great intensity of the 

 shadows, that the tubercles were visible on aU the species of Battle- 

 dore scales, but that they varied in size in almost every one of the 

 said species, being sometimes so small as easily to escape observa- 

 tion. I found the largest tubercles by far on the foreign specimen 

 sent to me by Mr. Mclntire, which scale I have sketched carefully.* 

 The tubercles measure the Wo o^h of an inch in length ; in Alexis 

 they are from ygwoth to To-g-^oth of an inch, while in many other 

 species, as " Long-tailed Blue," I did not make them more than 

 i 4oo- o th of an inch. 



Repeated observations have led me to recognize that the 

 tubercles are in all cases placed upon a distinctly -beaded but 

 narrow rib ; the base into which the little column seems to fit, 



* Dr. Anthony forwarded the sketch named, and the apjjearance is sub- 

 stantially the same as in the engraving illustrating his former paper. (See 

 the number for January, 1872.) 



VOL. VII. T 



