ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
123 
tween the water-jacket and the outer walls of the oven is filled with non- 
conducting earth X. 
In filling the water-jacket, water is poured in through a hole in the 
upper surface of the oven, until it begins to flow out from a side opening 
at a. 
To prevent the condensation of water, the chimney and side tube 
projecting from it are covered with a metal jacket m, which tends to 
reduce the cooling of the parts of the tube outside the oven. 
Fig. 13. 
The oven, finally, possesses an arrangement for ventilation by moist 
air. For this purpose the insulating jackets are cut through above and 
below at o and u. The upper opening is closed by two metal plates, 
which are pierced by two holes, and can be adjusted so that the holes fit 
over each other and give passage to the air, or not. The air entering 
from below passes over a box d d, in which a piece of moist linen l is 
stretched. The water for keeping this linen moist is supplied by an 
inverted Erlenmeyer flask b outside the oven, which is in communication 
with the box d d. 
Cultivating Protozoa.* — Prof. M. Ogata has obtained pure cultiva- 
tions of a few Infusoria, e. g. Polytoma uvella , Paramsecium aurelia , on 
* Centralbl. f. Bakteriol, u. Parasitenk,, xiv. (1893) pp. 165-9. 
