1885. ] Embryology. 615 
t 
was then observed in a number of ova, from which I infer that the 
peculiarity about to be described is charactistic of the develop- 
ment of this form. This species hatches in 24 to 36 hours. 
The accompanying figure represents the embryo lying on the 
surface of the vitellus, and is represented as foreshortened, anterior- 
ly the optic lobes, of of, on the other side 
of the vitellus show through the transparent 
yolk. e embryonic axis shows the seg- 
ments or somites, 7, distinctly developed, 
but it is very remarkable that the segmenta- 
tion does not end at the point where the 
axis of the embryo so far formed ends. 
The right and left limbs of the blastodermic 
rim form a X-shaped mass, together wit 
the embryonic axis anteriorly, but unlike 
any other normal teleostean embryo both 
these limbs of the rim are distinctly seg- 
‘mented for some distance as at m. 
Just within the yolk and a little in front 
of the yolk-blastopore, which runs forward into the acute angle 
formed by the limbs of the blastodermic rim, 47, lies the'large oil 
drop, o. A lozenge-shaped mass of cells lies in the acute angle 
of the 4-shaped terminal part of the embryo, which appears to 
contain or overlie Kupffer’s vesicle, Av, and what was assumed to 
be the chorda, c, at the time the observation was made, but of the 
certainty of this determination I am not at present satisfied. I 
was enabled to sketch this and a slightly more advanced stage 
several times, and as already stated found the same condition in 
a number of embryos, which seemed to be developing normally. 
Four other sketches show that the blastoderm finally closes very 
much as in other teleostean embryos and that pronounced wrink- 
les radiate from the crater-like opening upon the yolk where the 
yolk-blastopore finally disappears. 
The conclusions of His and Rauber to the effect that the em- 
bryonic axis is formed by the gradual fusion from before back- 
wards of the inner edges or the lips of the yolk-blastopore, as it 
advances over the surface of the vitelline globe, are in this case 
evidently correct, though it must be admitted that the presence 
of the cellular mass between the limbs of the blastodermic rim 
_ where they join the embryonic axis is not a little puzzling.— 
Sohn A. Ryder. 
THE MODE OF FORMATION AND THE MORPHOLOGICAL VALUE OF 
THE Ecc or Nera anD Notonecta.—In the last number of the 
Zeitschr. fiir wissenschaftl. Zoölogie, 1885, XLI. (p. 311), Ludwig 
Will has an article on this subject and reaches the rather startling 
conclusion that an egg-cell is not necessarily a simple protoplast, 
but may, while on the way towards the development of the ripe 
