Embryology. 659 
published, and on that account may be commended to the attention 
of students. 
N THE DEVELOPMENT OF THE COMMOM STURGEON. — Hav- 
ing been requested by the United States Fish Commissioner, 
Marshall MeDonald, to undertake the investigation of the stur- 
geon (Acipenser sturio), I repaired to Delaware City, Delaware, with 
that object in view. On the 15th of May mature eggs were 
found in a large female of that species, which was brought in to 
Mr. Anderson’s float. Fortunately a ripe male was encountered at 
the same time, also in a living condition, from which sufficient 
milt was obtained for the purpose of fertilizing the eggs. The 
eggs were quite free in the abdominal cavity, and they ran out 
in somewhat the way shot would pour out of a rent in a bag, as 
soon as the abdomen was cut open. The germinal disk was already 
formed ; in fact investigation disclosed the fact that the germinal 
disk, or area, is developed before the ovum leaves the follicle in 
- which it is matured. Two sorts of ova were found in different 
individuals. In some the eggs were brownish gray or olive, in 
other females the eggs were very much darker and contained far 
more pigment. In all of them, however, the germinal area was 
clearly defined at one side often with a distinct round dark spot 
marking its centre, with a paler ring surrounding the central dark 
area. External to the pale ring there was a distinct dark ring, 
followed on its external margin by anarrow pale band, from whence 
the color over the vegetative pole or yolk became uniform. In the 
darker variety of eggs some of these rings were not so distinct. 
uring the first hours of development but slight external changes 
were observed in the form of the germinal area, but by the second 
day this area had become distinctly oval; the central dark patch 
was oval and the marginal pigmented ring also oval. The eggs 
had also changed shape ; instead of remaining globular as they were 
at first, they assumed a slightly oval shape, the long axis of the 
oval lying parallel to the long axis of the now elongated germinal 
area. In the course of the third day the oval germinal area ha 
given place to one of somewhat different configuration. Instead of 
being oval, the germinal area now became decidedly more elongated 
and rounded at either end, and constricted at the middle, somewhat 
like the y of a violin. The medullary groove now me 
visible, and on the third day was distinctly apparent. On the 
fourth day the head, body and tail of the embryo had been differ- 
entiated so far as to project distinctly above the level of the oval 
yolk sack, the tail was in fact developing as a free, flat lobe. The 
heart could be seen pulsating within the thin-walled pericardiac 
