go General Notes. [January, 
nary dyes, after the use of nitric acid, is very difficult. This can 
be accomplished, however, in the following simple way: Add 
only a trace of nitric acid to the prepared section, and leave it 12- 
24 hours. The pigment dissolves slowly, and is taken up by the 
nuclei, and thus acts as a stain. The preparations are not beau- 
tiful, but are quite clear and distinct, and can be mounted without 
danger of disturbing the pigment. A similar proceeding (pig- 
ment dissolved by acetic acid) has been described by Leydig.’ 
The following is another mixture employed by Grenacher, as 
given by Carrière : 
Glycerine 
Alcohol (80 p. ee 2 
Hydrochloric aci 
pets 
The preparations remain in this mixture until the pigment 
changes color and becomes diffuse. 
METHOD oF EXAMINING THE REFLEX IN THE CompouND EYE 
oF InsEcTts.—Lowne® recommends the substitution of a reflecting 
ophthalmoscope for the eye-piece of a microscope. “ By this 
means a bright luminous spot may be observed as a real image 
in the tube of the instrument. A quarter objective must be used, 
and the mirror of the ophthalmoscope must be strongly illumi- 
nated. The microscope is then focused so that a real image of 
the corneal facets is seen between the objective and the eye of the 
observer. By bringing the object-zlass gradually nearer to the 
insect’s eye the reflex will come into view. The reflex appears 
as a disk having a fiery glow, in moths, and as a bright ruby spot 
in the cabbage butterfly. Sometimes six spots, surrounding a 
central spot, are seen in the eye of the insect; perhaps these are 
diffraction-images. A similar appearance is seen when the eye of 
this insect is observed by the naked eye, except that the spots 
are black. * * * The reflex seen with the micro-opthalmoscope 
is green in Tipula, and bright yellow in the diurnal flies. Colore 
diffraction-fringes are usually present around the central bright 
spot in both these insects; but the central image is sometimes 
surrounded by a perfectly black ring.” 
“ The manner in which the luminous reflex scintilates is very 
suggestive of an alteration in the focal plane of the dioptric struc- 
tures under the control of the insect.” 
The color of the reflex obtained is supposed to depend on the 
color of the fluid contents of the “ spindle” (“ Rhabdom” of Gren- 
acher), while the reflex itself is due to reflection from the spindles, 
which, in moths, are surrounded by very close parallel tracheal 
vessels, which form a very perfect reflector. 
The reflex disappears very quickly even in diffused daylight, 
1 Auge der Gliederthiere, p. 41. 
2 Die Sehorgane der Thieré, p. 205, 1885. 
3 Trans. Linn. Soc. Lond. Second Ser., Zoology. Vol. 11. Part 2, p. 406-7- 
Dec., 1884. 
