264 H. Rathke on the Metamorphosis of the Crustacea. 
disappears in the ambulatory feet, the appendage which they 
bear subsequently falling off. The foot-jaws of the anterior 
pair are already like those of full-grown specimens. Branchiz 
are already present on the legs and behind the foot-jaws, but 
they are still very small, and at the utmost merely provided 
with small low warts on their surface. The tail or abdomen 
possesses as yet no false feet, and the fan consists merely of a 
single almost triangular lamina of considerable size, the pos- 
terior margin of which has a slight incisure (ausschnitt), and 
whose lateral halves are so applied together inferiorly, that they, 
for the most part, touch each other. The front antenna con- 
sists, it is true, of several articulations, but is not yet sepa- 
rated into two branches, The posterior antenna is not much 
longer, but consists of two branches nearly equal in length, 
of which the one represents a pretty broad lamina (appendix), 
the other a cylinder (walze). In front a simple nearly subu- 
late snout proceeds from the cephalothorax, which is, at least, 
as long as the front or smaller antenna, and curves between 
the eyes downwards. 
2. Pagurus Bernhardus.—Embryos about to escape, have 
only three pairs of members that can serve for locomotion. 
The front pair is the longest, the central somewhat shorter, 
the hinder about half as long as the central. This hinder 
member consists of three articulations unequal in size, but is 
otherwise simple. On the other hand, each of the four other 
members consists of a rather long and thickish stem, and of 
two branches of nearly equal length, which originate near one 
another at the lower end of the stem, and one of which is 
situated exteriorly to the other; the outer one is (flat) com- 
pressed, and is composed of two articulations, the inner one is 
cylindrical and composed of five articulations. All these six 
members are not, as might be expected, true feet in a lower 
stage of development, but, as will appear hereafter, the foot- 
jaws; and indeed their maxillz and mandibulz are apparent, 
but they offer nothing particularly remarkable. Of true legs, 
and also of branchiz, there does not yet exist a trace. The 
antenne are similarly constituted to those in the mature em- 
bryos of the Lobster. In front a thin and moderately long 
snout proceeds from the cephalothorax. The tail is long, thin, 
and distinctly articulated. False feet are not yet observable. 
Only the central lamina of the fan is present, and represents 
a simple lamina narrow in front, posteriorly considerably 
broad, the two hind corners of which are somewhat rounded, 
and the posterior margin furnished with a slight incisure. 
In young, which are 1 lin. in length, and considerably larger 
than the mature embryos, the four anterior foot-jaws were of 
