PRACTICAL PROCESSES IN VEGETABLE HISTOLOGY, 331 
I have tried Yo repeat this experiment during September and 
October, but have failed to do so on account of the cold. 
In conclusion, I wish to state what I have observed since the 
first part of this paper has appeared in print. 
On three separate occasions I have noticed a very large Hydra, 
entirely covered with sperm sacs; and surrounding this polype 
were several others with ovaries only, no sperm sacs being visible. 
The bursting of the ovaries occurred at the same time in all the 
Hydre. In some cases two eggs were produced, and at the same 
time the Hydra covered with the sperm sacs poured out the sper- 
matozoa in abundance; and this continued for six hours. ‘The 
eggs remained attached to the Hydra for three days, when, finally, 
they dropped off and fell to the bottom of the tank. 
PRACTICAL, PROCESSES IN VEGERABLE 
HISTOLOGY. . 
By L. OLIver, in Rey. Sci. Nat., 1882. 
Taken from the Journal of the Royal Microscopical Society. 
(Concluded from page 322.) 
Acetic acid.—The effect of this acid is very perceptible when care 
is taken to wash the preparations in distilled water before sub- 
mitting them to its action. It assists the examination of the nuclei, 
which it renders more visible, chiefly by effect of contrast, render- 
ing the protoplasm which surrounds them soluble in the water. 
Carbolic actd.— E. Warming, whose interesting work on bacteria 
and monads is well known, has found in carbolic acid a valuable 
agent for rendering these little organisms transparent. 
Alcohol and Nitric acid —We haye obtained preparations of 
extreme thinness and of the greatest transparency* in the following 
manner :—Place in a watch-glass the objects to be thinned (sec- 
tions of stems or roots) ; add to them alcohol of 36°, into which 
pour, drop by drop, concentrated nitric acid until the red vapours 
of hyponitric acid are disengaged. If the preparations are violently 
attacked, cover the watch-glass with a small bell-glass, observing 
through it what takes place in the liquid; as soon as the prepar- 
ations rise to the surface of the mixture raise the cover, and by 
means of two wooden needles push them to the bottom of the glass. 
* © Recherches sur l’appareil tégumentaire des racines’ (8 pls, and 50 micros 
photographs). Paris, 1881. 
