218 THE ENTOMOLOGIST. 
inner and the other the outer surface. From this simple 
preparation one can see all that is necessary, for the useful 
differential characters reside in the chitinous and not in the 
membranous parts; and the structures thus mounted present 
a certain amount of what may be called ‘‘ character,” arising 
no doubt from the retention of much of the natural orientation 
of the parts, which is entirely lost when they are treated with 
chemicals and embedded in a transparent medium. The 
cleansing and dissection can easily be accomplished with the 
aid of a hand-lens, magnifying ten diameters or less, mounted 
on a home-made stand of some sort, and if a greater magnifica- 
tion is desired for subsequent examination, hand-lenses x 20 are 
common nowadays; but none of these equal in definition a good 
4 in. microscope objective used as a hand-lens. If there are any 
distinctive characters in the male genitalia of a lepidopteron, a dry- 
mounted preparation will show them to an extent quite impossible 
in a slide; and the minutiz for the examination of which a slide- 
preparation is really necessary are not of the first importance 
from a taxonomic point of view. The great defect of slide- 
preparations, which anyone except a microscope man can see, 
is that we are limited to one aspect of the object only, that 
at right angles to the plane in which the slide lies. If it were 
necessary to demonstrate the utter futility in certain cases of 
slide-preparations as a means of illustrating the form and 
arrangement of the parts, H. melotis might well be quoted as ° 
a case in point. In this species the edeagus-guides in the 
lateral aspect form two long branches from a wide base, the 
upper bisinuate and gradually pointed, the lower nearly straight 
for two-thirds of its length, the pointed apical third being 
suddenly bent back on the upper side of the remainder ; this 
recurved portion is, in fact, one end of a trisinuate chitinous 
bar which reaches from side to side and is fused with the end 
of the lower branch. This bar is best seen in the ventro- 
cephalad aspect, when it presents a remarkable resemblance to 
a well-developed pair of oxen horns. In Prof. Reverdin’s figure 
(‘Bull. Soc. Lep. de Genéve,’ ii, t. 18, fig. 3), which is as good 
a reproduction of an excellent slide-preparation as | ever expect 
to see, the ends of the bar appear as half-crescent-shaped bodies 
with their concavity behind, and the real nature of the bar is 
not indicated. 
There has lately been a good deal of discussion as to the best 
means of rendering intelligible to others the results of one’s 
examination of genitalia; the reproduction of photographs is 
advocated by some, and of diagrams by others, in both cases from 
slide-preparations. It is claimed that the photographs must, in 
the nature of things, be accurate; but the advocates of this 
method seem to forget that accurate photographic representation 
of a slide-preparation is at any one time limited to one plane of 
