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. Branchiae 

 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 maxillae and mandibular are apparent, 

 but they offer nothing particularly remarkable. Of true legs, 

 and also of branchiae, there does not yet exist a trace. The 

 antennae 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 l^lin. in length, and considerably larger 

 than the mature embryos, the four anterior foot-jaws were of 



