1886.] Embryology. 739 
and the black grouse (Tetrao tetrix). Most of the thirteen speci- 
mens examined were males 
Mammals—Mr. Frederick True, in a letter to Science, asserts 
that he has found characters by which Lynx canadensis can be 
distinguished from Z. rufus and the other Southern varieties. Ex- 
amination of over sixty skulls showed that in all examples of 
. canadensis the anterior condyloid foramen is zo¢ confluent with 
i the foramen lacerum posterium, and that the visible portion, of 
the presphenoid is flask-shaped, the convexity in front. 
L. rufus, maculatus and fasciatus the two foramina are confluent 
as in the cats generally, and the visible part of the presphenoid is 
sagittate or linear. Mr. True, therefore, believes that there are 
two species of American lynxes, and that the confluence of the 
condyloid and lacerated foramina cannot in future be regarded 
as a distinguishing character of the Æluroidea. Walter Heape 
(Quart, Jour. Mic. Science, Feb., 1886) contributes an article 
upon the development of the mole (Talpa europea), the 
Ovarian ovum and the segmentation of the ovum. The 
remaining portion of the inner mass, and the mesoblast, subse- 
quently, from both epiblast and hypoblast layers. Thus the 
division of the segmentation spheres, by Beneden, into epi- and 
hypoblast spheres from the time when the two first segments 
were formed, is incorrect. Dr. O. Finsch has recently described 
a new species of wild pig (Sus niger) from New Guinea. 
EMBRYOLOGY." 
THE METAMORPHOSIS OF THE AMERICAN LOBSTER, Homarus 
AMERICANUS H. Mitne-EpwArps. — The changes which the 
young lobster undergoes during the first six or seven weeks of its _ 
free existence, as a pelagic organism, constitute a veritable met- 
amorphosis, which is apparently accomplished in the course of six _ 
ecdyses, or changes of the exoskeletal investment of the body. 
ese molts, or ecdyses, occur at intervals of from four to fif- 
teen or more days, if the larve are well fed. At each ecdysis a 
complete renewal of the exoskeleton occurs; the old cast skin = 
ng quite thin and transparent up to the fifth ecdysis, and retains 
the form of the body at the time of molting. The old skin is rup- 
| oa along the median dorsal line of the cephalothorax and at 
te point where the latter joins the abdomen; the tail is with- 
drawn after the head. esos a 
uch as some Arthropods undergo an ecdysis within the 
“SS, the advanced eggs of the lobster have been carefully exam- _ 
med to determine whether a molt took place at the time of - 
“Edited by JoHN A. RYDER, Smithsonian Institution, Washington, D. C. 
ey 
