Royal Microscopical Society. 261 



face of the recent scale, so as to denude the ribs. Fig. 32 accom- 

 panied his remarks of date January 1, 1871.* This would place a 

 pigmentary deposit outside the scale, and this portion I feel dis- 

 posed to regard either as an exudation of the material within, 

 through the scale membranes, or as the remains of the moisture 

 with which the wings are clothed at the time of emergence from 

 the chrysalis state, rather than as possessing any cellular structure 

 outside the scale. Hence the term here, " pigment cells," seems to 

 be objectionable. Where it existed in a finely granular condition 

 within the substance of the scale, or on the boundaries of the areas 

 produced by the framework, the term " cell " seems less suited ; 

 but when in particular spots, or patches of any size, it may seem 

 more applicable, though by transmitted light it becomes most diffi- 

 cult to determine what is due to interference and what to accumu- 

 lation of coloured material. By the term "pigment cells" we 

 virtually admit their cellular nature ; thus it seems open to ob- 

 jection, seeing the term beads is also suh judice. Perhajos it would 

 be better to speak of pigment granules where they can be seen as 

 so many separate fine dark or coloured specks in the membranes 

 and edges of the framework of the dark or coloured scales, and pig- 

 mentary deposit where a coloured irregular layer can be found in or 

 on the normal free surfaces. Mr. Mclntire, in his correspondence, 

 which I take the liberty to quote, suggests " this material never 

 thoroughly dries, and rough usage would modify its appearance " : 

 hence perhaps it could be better studied as an opaque object, though 

 a very tedious process with high powers ; certainly torrefaction does 

 not much aid in its displacement, and finding this, I hoped more 

 from the use of strong sulphuric and nitric acids, but was disap- 

 pointed: other reagents may eventually aid in its study, for opti- 

 cally it is feared we shall not arrive at anything very definite. 

 For those scales which are nearly transparent, and where pigment, 

 as such, not necessarily of a dark colour, exists in a highly granular 

 condition, I would suggest that it should in such scales pass by the 

 name of pale granular pigment, or short, pale granules, and where 

 external, pale granular deposit, wliich would embrace those scales 

 which are of a silvery or pearly-opaque aspect, or which may be of 

 a dead white, varying to any tint of a light colour, even to brick 



* " I enclose yon a pencil sketch of part of a scale of the Humming-bird Sphinx. 

 I took the scales with my finger made quite dry from the living insect, then placed 

 them on a clean piece of glass, and took anotlier piece and pressed it upon the first, 

 and gave it a roughisli slide on the otlier; then examined tlie ill-used scales with 

 my ith object-glass, corrected for uncovered objects. The scale from which I took 

 the sketch was from the first, therefore the surface seen was the upper surface : 

 you will see that the rough treatment has luckily abraded the cuticle, if we may 

 so call it, on both sides, leaving the internal bars in places quite clean. The 

 under side is the same as the upper as seen in anotlier scale." My views make 

 the outer membrane or surface as the most transparent, and tlie inner as the chief 

 pigmentary membrane. 



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