118 Dr Rn scorn's Observations on the Natural History 
of this species is represented in the act of laying her egg ; and 
the letter a of the same figure shews a leaf folded down, in 
which an egg has been laid. 
The egg thus deposited on the leaf, is committed to Nature to 
carry forward its several stages of evolution ; and these the 
author next proceeds to describe. In the^ plate, the whole se- 
ries of appearances is exhibited as they occur in the egg of the 
Salamandra platycauda ; and, in order to make known the dif- 
ferent epochs of development, and the intervals between them, 
by a simple inspection of the plate, without recurring to the ex- 
planation, the figures are marked, in succession, by the dates of 
the days in which the designs have been made. Thus the fi- 
gure marked 23d April, exhibits the egg of its natural size, and 
the figure below it, the same egg magnified. It was collected 
immediately after being deposited, and kept always in the water, 
and on its proper leaf. During the period of observation, the 
temperature of the water varied from 22° to 27° of the Centi- 
grade scale. The globule in the centre is white, with a tint of 
yellow : it is surrounded by a glairy matter, to which it is no 
where attached ; so that it is able to move freely in every direc- 
tion : its envelope is membranous, transparent as glass, and co- 
vered with a kind of very limpid viscid matter. If one of these 
eggs, with its envelope, be placed on a dish, and if, with the point 
of a fine brush, its envelope be turned, so that the upper part 
shall be made to look downward, the globule presently turns on 
its axis, in such a way that it presents anew the surface which 
was at first uppermost, which proves that its density is not uni- 
form. This phenomenon is still more readily seen in the eggs of 
the Salamandra exigua , because they are brown on one side 
and white on the other. If, instead of turning the egg, we ele- 
vate one of its ends, so that its longitudinal diameter shall be per- 
pendicular to the horizon, the globule, which was in the middle, 
falls to the bottom of the glairy matter, which demonstrates that 
the specific gravity of that matter is less than that of the globule. 
Fig. 26th April exhibits the changes which the globule has 
undergone in the short space of three days. Examining it with 
the microscope, one suspects already what are the parts of the 
embryo which become, in the sequel, the belly, the head, and 
ithe tail. At first the globule enlarges, then elongates, and its 
