468 EYVCLESHYMER. [Vor. XIV. 
During the spring of 1895 similar experiments were made on 
the eggs of Acris and Bufo, and those made on the eggs of 
Amblystoma were repeated and extended. 
Given areas were marked by the method used in the earlier 
work, which was briefly as follows: The outer envelopes are 
removed from the egg, which is then placed in a watch crystal, 
on a bed of cotton, with barely enough water to cover it. The 
egg is then rotated until the desired point is uppermost, when 
it is punctured with an extremely fine hair held by forceps. A 
small quantity of the protoplasm oozes out and forms a minute 
exovate, which remains attached to the egg. The eggs thus 
marked are transferred to watch crystals, in which they remain 
until the embryo is formed. A large mirror is fastened to the 
stage of a dissecting microscope; on this the watch crystals are 
arranged in series, and the eggs examined by means of an 
extension arm. The image of the opposite side may be thus 
observed during the entire period, from the time of marking 
until the embryo is formed. 
The removal of the envelopes is necessary, since it is other- 
wise impossible to prevent the rotation of the egg, often result- 
ing in the detachment of the exovate. If it be argued that the 
course of development is thus diverted, I reply by saying that 
I have compared the phases of cleavage and embryo formation 
in eggs from which the envelopes had been removed, with 
those in which the membranes were intact, and can positively 
assert that in these stages no visible disturbances are induced. 
In marking the eggs, great care is imperative, since a severe 
puncture invariably results in the formation of a large exovate, 
which necessarily obscures normal development; again, the 
puncture may be so slight that the injured portion heals, and 
the mark is entirely obliterated. 
Series I.— Acris grillus. 
On March 28, 1895, twenty-five eggs of Acris were selected, 
in which the second cleavage grooves were just forming. From 
these the envelopes were removed, and the eggs punctured at 
the point where the first and second cleavage grooves crossed. 
The eggs were then transferred to watch glasses, and examined 
