8 Transactions of the Royal Microscopical Society. 
Il.—A Stage Incubator. By H. A. Rerves, Assistant-Surgeon 
and Teacher of Practical Surgery, London Hospital. 
(Taken as read before the Royau Microscopicau Society, December 6, 1876.) 
Ir is much to be desired that the various processes of elementary 
tissue change and of development and growth should be observed 
under the microscope. To this end I have devised the followmg 
simple apparatus, which, as will be seen, is a modification of the 
Stricker-Sanderson hot stage, with the gas-tubes omitted. The 
central cell, which is larger and ovoid, is only excavated to a depth 
sufficient to allow of a pigeon’s, or smaller egg, as of sparrow, 
canary, &c., being admitted, and is continuous beneath the egg to 
permit of the circulation of the hot water. The accompanying 
woodcut, Fig. 1, represents a section of the incubator, the inter- 
rupted line being the cover-glass, and E the egg with its shell and 
fibrous covering removed sufficiently to expose the blastoderm. 
The space between the egg and the apparatus should be packed 
with cotton wool to retain the heat, and to prevent injury to the 
egg. If found necessary a little sulphuric acid can be dropped on 
the wool to prevent the condensation of vapour on the cover-glass. 
Page’s gas regulator should be employed to keep the feeding water- 
containing vessel at a constant temperature, which can be watched 
by the attached thermometer. I hope that this simple instrument, 
permitting, as I believe it will, of the observation of the blastoderm, 
as an opaque object, for hours and days, may be of solid service in 
embryology. 
It is obvious that by increasing the size of the instrument, a 
hen’s or duck’s egg could be accommodated ; and if the excavation 
for the egg were carried quite through the centre of the incubator 
—hbut not at the sides—and enough of the shell removed from the 
lower side of the egg, I think the blastoderm and yolk could be 
