122 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
while the object-holder formed the back wall, and a cover-glass, 
30 by 40 mm., the front wall. The whole apparatus was fastened by 
clamps on the stage of a horizontally inclined Microscope. This 
aquarium could thus be very easily made ; but it had the drawback, 
which made itself especially felt in embryological investigations, that 
it only allowed of observations being made from the side of the front wall. 
On this account, in the new form of apparatus the aquarium proper 
is detachable from the holder. As seen in fig. 12, the aquarium A 
consists of a strip of glass 8 mm. broad, bent into the form | 1 , which 
serves as side-walls and bottom, and of two cover-glasses, 30 by 40 mm., 
which are cemented by Canada balsam to the glass strip and form the 
front and back walls. 
The holder T for the reception of the aquarium consists of a metal 
plate of dimensions 4 by 9 cm. with a large rectangular aperture, on the 
sides of which two strips of metal bent at right angles are riveted. In 
the frame R thus formed, which is provided with two springs, the 
aquarium is inserted with either cover-glass in front, so that creatures 
which have attached themselves to either one or the other cover-glass 
can be brought under observation. 
Apparatus for Regulating the Temperature of Hatching-Ovens, &c.* 
— Herr A. Koch describes the method of regulating the temperature 
made use of in the hatching-ovens supplied by Sartorius of Gottingen. 
For this purpose there is in the interior of the oven a metal capsule con- 
taining a liquid, with a high co-efficient of expansion, which, as the 
temperature rises, causes the walls of the capsule to bulge outwards. 
This has the effect of raising the rod S (fig. 13) which rests upon it. 
This rod then acts upon the lever j g h , from the free end of which h 
hangs a chain, carrying a cover d , which fits over the chimney s of the 
heating apparatus. From the side of the chimney projects at right 
angles a tube c, which traverses the water-jacket of the oven and emerges 
again near the place where it entered. 
When the cover d closes the top of the chimney, the hot air from 
the flame passes into the horizontal tube and warms the water of the 
oven. As the temperature in the interior rises up to a certain point, 
the capsule Jc (represented more particularly at B) expands until the 
rod S acts on the adjusting screw j of the lever, and the cover is lifted 
off the chimney. As soon as this happens the hot air from the flame 
passes out freely from the upper end of the chimney s, and ceases to 
warm the oven. The latter therefore begins to cool, the capsule works 
in the opposite way, the cover closes over the chimney, and the oven is 
again heated. 
The adjustment of the apparatus for definite temperatures is easily 
effected by means of the adjusting screw j of the lever, and the sliding 
weight g , which can be fixed in any position on the arm. The apparatus 
allows of temperatures from 20° to 70° being kept constant, but for the 
production of the different temperatures, in all, six different capsules Jc , 
each covering an interval of 10°, are necessary. 
To prevent, as far as possible, the apparatus from being affected by 
the variations in temperature of the surrounding air, the space be- 
* Zeitschr. f. wiss. Mikr., x. (189?) pp. 161-4. 
