120 University of California Publications in Zoology [Vou.9 
contact with the curved floor of the cell below and the cover- 
glass above. The current, if strong enough, causes a slight fiat- 
tening of the eggs, but can be so regulated that the eggs are 
held without distortion against the under side of the cover-glass. 
Under such conditions they may be studied with an oil immer- 
sion lens. 
A slide such as the one just described can easily be modified 
to make it available for many kiftds of cultural and experimental 
work, whether with gases, fluids or electric currents. It can also 
be used for fixing and staining under the microscope. 
For convenience in quickly changing the fluids to be passed 
through the slide a number of small glass stoppered bottles are 
supported (by having their necks let into slots) on the rim of 
a circular wooden dise, which may be both rotated about a 
vertical axis and also raised or lowered on the central shaft. 
Plates 16 and 17 show the bottles as they are used, and figure M 
is a vertical section showing the construction of the parts sup- 
porting the disc. The rod (rd.) has along one side a groove 
(gr.). in which a pin (pin) of the sleeve (s/.) fits. The sleeve 
has at its lower end a flange, which rests on a spiral spring and 
Fig. M. Section of metal supporting parts of the center of dise for 
holding reagent bottles. Xx 14. 
cl., collar and set-serew; disc, wooden dise; d. sl., metal sleeve to which 
dise is attached; gr., groove; pin, pin; rd., central supporting rod; sl., 
sleeve resting on spiral spring and about which the sleeve (d. sl.) may 
rotate—it may move vertically, but is prevented from rotating by the pin. 
