722 General Notes. [July, 
of cream, without perceptible odor, and with the flavor of cocoa- 
nut milk. The fishermen state that this species, which is the one 
most common on the Atlantic coast, cannot remain under water 
more than four or five minutes. The color of the back, in some 
examples taken at Cape May Point, was a light plumbeous tint, 
but it appears that the depth of the color varies in different indi- 
viduals, and deepens rapidly after life is extinct, especially if the 
specimens lie in the sun. 
M. Paul Albrecht, in the Pressé Medicale Belge, 1884 (October), 
states that there are fourteen digits in the vertebrate foét. Seven 
of these are radial and tibial, one is axial, and six are ulnar and 
fibular. 
M. Retterer, in a thesis presented to the Faculty of Sciences of 
Paris, describes the early stages of the limbs and feet in various 
mammalia. e shows that the primitive cartilages display the 
same numbers and character as the bones of the adults in a great 
many cases, 
EMBRYOLOGY.! 
On THE EMBRYOLOGY OF LimuLus POLYPHEMUS? III. — The 
stage under examination is that represented on Figs. 12 and 13, 
14 and 15 (Plates 111 and 1v) of my essay on the development of 
Limulus (Memoirs Boston Society Natural History, 1872). At 
this stage the oval blastodermic disc, with the six pairs of the 
cephalic appendages, is distinctly formed; the mouth is seen in a 
position in front of the first pair of appendages, and from it the 
primitive streak passes back to the posterior margin of the blas- 
todermic disc or “ventral plate.” The abdomen is separated 
from the head by a curved groove, as seen in Fig. 12 of my 
memoir. 
nature of the embryonic membrane, which I had previously re- 
garded as the homologue of the amnion, and afterwards as the 
serous membrane of insects, but which Mr. J. S. Kingsley’ has 
found to be secreted from the blastoderm. A thin section (Plate 
xxIv, Figs. 1 and 5) shows that the membrane is very thick, struc- 
tureless, the cellular appearance being confined to the external 
surface. This membrane is evidently secreted by the blastoderm ; 
the irregular cell-like markings (see my second memoir, 1880, 
Pl, i, Figs. 14, 144, 14¢, 14d) are, so to speak, casts of the blas- 
toderm , which with the marks of even their nuclei are im- 
__ pressed upon the membrane during the early stage in its forma- 
= Edited by Jonn A. RYDER, Smithsonian Institution, Washington, D. C. 
. — *Read before the American Philosophical Society, January 16, 1885. 
“The Development of Limulus, Science Record, 11, pp. 249-251, Sept., 1884. 
