ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
223 
tions are placed so as to be viewed conveniently, and have verniers 
reading to tenths of a millimetre. 
Fig. 55. 
(3) Illuminating- and other Apparatus. 
Hartnack’s Embryograph. — This instrument is mainly a more com- 
pact form of one designed by Prcfessor His, of Leipzig, and is intended 
for outline drawing under low powers, with the advantage of changing 
-easily from a given scale to any other. One of Oberhauser’s cameras is 
combined with a small photographic objective of such a kind that both 
these articles can be moved up and down on a 60 cm. long, graduated 
guide-bar T, and their mutual distance can be altered within comfortable 
limits. The foot of the guide-bar bears the sliding object-table and 
below that a Microscope mirror. 
Fig. 56 shows the instrument mounted on a foot-board ; but this is 
now replaced by an iron foot, thus increasing the stability. The ground- 
glass plate G serves as the drawing surface, and is placed at a suitable 
