ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
101 
of the movement is effected by a dove-tail bar attached to a lower 
portion of the frame and is completely covered. The amount of the 
movement of the lateral position of the frame can be read by scale S L 
and vernier N x . 
The milled head W projecting from the side of the stage is connected 
with a pinion, working a rack attached to the under side of the stage T 
on the right, and effects the forward and backward movement of the 
stage. The stage is made to move accurately and smoothly by means of 
two guide strips (not visible in the illustration). The four strips rising 
from the base shown in the figure are ground perfectly plane and smooth 
and serve as sliding surfaces for the guides. The magnitude of the 
movement is read off scale S 2 by means of vernier N 2 . The range of the 
movement in this direction is 35 mm. The milled head W also serves as 
a handle for rotating the entire stage. 
The movable stage disc T is provided with an oval slot running in 
the direction of the movement. This slot is conically expanded down- 
wards, and the base-plate G, which remains in a fixed position on the 
Microscope, has a circular opening in the centre. The arrangement 
admits of contact being established between the object-slide and the 
front surface of the condenser at any position of the stage. The makers 
state that all sensitive parts are well protected from dust and other 
influences. To set free the entire surface of the Microscope stage, 
unscrew the small vertical head L, and the whole frame B, which is fixed 
in position by two set-pins and held down by this screw, may be lifted 
olf, and the stage then presents the appearance shown in fig. 9. 
'The stage is sufficiently large to take a culture plate or dish, or an 
object-slide of any desired form may be fixed by means of the spring- 
clips FF. 
The stage is attached to the stand (fig. 10) and detached from it in 
precisely the same manner as in the case of the older stage. 
(3) Illuminating; and other Apparatus. 
Differential Object-carrier.* — Dr. H. E. Hildebrand has devised 
a new form of object-carrier for use in morphological work, where 
moving living objects are being studied. It allows, without changing 
the position of the guiding hand, both of constant tracks being kept, as 
in the ordinary mechanical stage, and also of any movements required 
by the object being given. This is effected by a difference in the 
friction between the surfaces for the back and front movement and 
those for the side to side movement. This difference in the friction 
can be ignored by the guiding hand in the production of any desired 
movement, but is allowed to control the motion when constant tracks 
are to be described. 
The object-carrier consists essentially of a plate with central aperture 
lying across the Microscope-stage, which is provided with a pressure 
spring, and by means of a grooved head can be rotated about a stationary 
vertical rod and also displaced laterally. 
The steel rod x (Fig. 11), as the axis of all movements, is firmly 
fixed in its base-plate, the T-piece T, wdiich is of such a length that 
* Zeitschr. f. wiss. Mikr., xi. (1894) pp. 304-12. 
