THE YOUNG 
would be otherwise invisible, and we will 
be thus enabled to assign them their proper 
place in the great system of classification. 
By it, too, may be studied the habits and 
life-history of the majority of the animal- 
cules found in liquids. 
That these statements are not exagger- 
ated is shown by the fact that some of the 
most important discoveries have been made 
by means of microscopes far inferior to 
those that can now be had for ^20. Indeed, 
much of the work of the great Ehrenberg 
was done with a microscope which to-day 
would not command $25. Therefore, let 
not the owners of cheap microscopes 
despair, for the field which is open to them 
is sufficient to occupy the longest life, and 
te employ the highest powers. 
The Weber Slide. 
fTlHEBE is no doubt in the minds of 
those who use the microscope that 
living objects, whether animal or vegetable, 
are by far the most interesting, especially 
to beginners, and a simple and inexpensive 
means of preserving and exhibiting them 
has long been a desideratum. The well- 
known live-box or animalcule cage serves 
the purpose very well, but it is expensive, 
and does not entirely prevent the evapor- 
ation of the liquid in which the objects are 
contained. The ordinary concave slide, 
B 
THE WEBEB SLIDE. 
though better than a plain slip of glass, 
does not fulfil all the requirements, and 
with such a slide it is difficult to keep the 
object in focus, except with very low powers. 
To obviate these difficulties, Mr. Weber 
has reversed the form of the cell, and forms 
his slide as shown in the accompanying en- 
graving, where A is the convex bottom of 
the cell, and B the thin glass cover — a drop 
of water being held between them by capil- 
lary attraction. When the cover is ce- 
mented down by means of a little water- 
I 
SCIENTIST. 145 
proof cement, the water cannot evaporate, 
and the whole arrangement forms an air- 
tight aquarium on a minute scale. The 
open space forms a chamber which retains 
a supply of air, and if the animal and vege- 
table life are properly balanced, life may 
exist in one of these slides for weeks. In- 
deed we have been surprised at the length 
of time that they keep in good condition. 
In the engraving, which shows the slide 
as manufactured by Mr. C. F. Prentice, of 
this city, the thickness of the slide, etc. , is 
magnified about four times. 
Volvox Globator. 
AEECENT English writer tells us thai 
the most popular objects amongst the 
amateur microscopists of his country are 
the Volvox globator and the Conochilus, and 
there can be no question that they deserve 
all the attention that has been bestowed 
upon them. Fortunately they are both 
found in the ponds of this country, so that 
we feel certain that our readers who will 
carefully seek for them will be pretty sure 
to find them. During the past few years^ 
the life-history of the Volvox has been very 
carefully and thoroughly worked out, and 
those who desire to study it will find a very 
excellent article by Prof. Alfred W. Ben- 
nett, in a recent number of the American 
Journal of Microscopy. But as this article 
is very elaborate, we have thought it well 
to prepare the following simple descriptioB 
for the benefit of our younger readers. 
When first discovered by Leeuwenhoek, 
about two hundred years ago, it was re- 
garded as an animal, and even now the un- 
educated observer can hardly believe that 
it is a vegetable. Such it is, however, de- 
spite its power of locomotion, and its very 
peculiar and beautiful form. The reader 
must bear in mind that there are many 
minute plants that have the power of mov- 
ing through the water in which they live — 
some of them with considerable speed. 
The usual appearance of the Volvox is 
very well shown in our engraving. Under 
a moderate power, it appears as a pale green 
globe covered with dots, from each of 
