1887] Microscopy. 401 
Poa No affirmative evidence mentioned. Gray, Lesley, Dana, 
ould. 
B. ae derived from revelation. Young, Cook, Hill, 
4. Palen from science affirmative (5). 
A. No evidence cited. A. Hall. 
B. Evidence psychophysical. Pierce, Cope. 
c. Evidence spiritualistic. Wallace, Coues. 
MICROSCOPY. 
EYES OF MOLLUSCS AND ARTHROPODS.? 
weet 2: of Young Pectens from 1-3 mm. long. I. MoL- 
LUSCS.—I. Specimens are placed in a mixture of equal parts 
of eae and picro-sulphuric acid. After ten or fifteen 
minutes they are washed in thirty-five per cent. and seventy per 
ey: of alcoho 
The shells are then opened and the mantle dissected out 
with needles. Thus treated, the shape of the mantle is well pre- 
served, whereas if removed ‘before hardening it becomes much 
coiled and twisted. 
3. Each mantle edge may be cut, according to its size an 
curvature, into three or four pieces, and these will then lie suf- 
ficiently straight for convenient sectionin 
t is necessary to use a different reagent for nearly every part 
of the eye. 
The Rods.—Chromic acid gives the most varied results accord- 
ing to the strength, time of action, and temperature of the solu- 
tion, or by various combinations of these three. For instance, 
one-twentieth to one-fifth per cent. for thirty to forty hours failed 
to give any conception of the structure of the rods, while other 
parts of the retina, and of the eye itself, were well preserved ; 
but when allowed to act for half an hour at a temperature of 
from 50° to 55° C., perfectly preserved rods with their nervous 
net-works are = ained, while, on the other hand, the remaining 
tissues becom o granular and homogeneous as to be unfit for 
study. This jater asi allows the rods to be removed in flakes 
and their ends examined without the aid of sections. Jz is only 
in this way that the axial nerve-loops can be observed. 
The Lens—The lens is best prepared for sections by either 
. sulphu ric or picro-sulphuric acid; by the first reagent its shape 
is best retained, and the lens itself is less liable to be drawn away 
from the surrounding tissue ; set reagent, however, brings 
out more sharply the configurat on of the cells and allows a 
better stain of the nuclei to take place. 
The Retinophore.—The retinophore are well preserved by 
nearly all the reagents; but in sublimate, in aps acid, or in 
2 Edited by C. O. WHITMAN, Ph.D., Milwaukee, Wisconsin. 
. 2 Dr. Wm. Patten, Mitth. a. d. Zodl. Station z. Neapel, vi. p- 733, 1886. 
