4 SL I. Smith — Early stages of the Lobster. 



than in the first stage, and have become truly cheliform. The 

 succeeding legs have changed little. The epidodi of all the 

 legs and of the external maxillipeds have increased in size, and 

 the branchial processes are distinctly lobed along the edges, and 

 have begun to assume the form of true branchiae. The seg- 

 ments of the abdomen have the same number of spines but they 

 are relatively somewhat smaller, and the last segment is rela- 

 tively smaller and broader at base. The appendages of the 

 second to the fifth segments differ considerably in size in differ- 

 ent specimens, but are nearly as long as the segments them- 

 selves ; their terminal lamellae, however, are represented only 

 by simple sack-like appendages, without sign of segmentation, 

 or clothing of hairs or setae. The penultimate segment is still 

 without appendages. 



Third Stage. — In the third stage (pi. IX, figs. F, F, O) the 

 larvae are about half an inch (12 to 13 nmi ) in length, and the 

 integument is of a much firmer consistency than in the earlier 

 stages. The antennulae are still rudimentary, and considerably 

 shorter than the rostrum, although the secondary flagellum has 

 increased in length, and begins to show division into numer- 

 ous segments. The antennae retain the most marked feature of 

 the early stages — the large size of the scale — but the flagellum 

 is much longer than the scale, and begins to show division 

 into segments. The mandibles, maxillae, and first and second 

 maxillipeds have changed very little, although in the second 

 maxillipeds, the extremity of the exognathus begins to assume 

 a fiagelliform character, and the branchia is represented by a 

 small process upon the side of the epignathus. The maxilli- 

 peds have begun to lose their pediform character. The anterior 

 legs have increased enormously in size, and those of the second 

 and third pairs have become truly chelate, while the swimming 

 exopodal branches of all the legs, as well as of the external 

 maxillipeds, are relatively much smaller and more unimportant. 

 The epipodi (fig. D) are furnished with hairs along the edges, 

 and begin to assume the characters of these appendages in the 

 adult. The branchiae (fig. D) have developed rapidly, and 

 have a single series of well-marked lobes along each side. 

 The abdomen still has the spines characteristic of the earlier 

 stages, though all of them are much reduced in size. The 

 appendages of the second to the fifth segments have become 

 conspicuous, their lamellae have more than doubled in length, 

 and the margins of the terminal half are furnished with very 

 short ciliated setae. The appendages of the penultimate seg- 

 ment (fig. F) are well developed, although quite different from 

 those in the adult. The outer lamella wants wholly the trans- 

 verse articulation near its extremity, and both are margined, 

 except the outer edge of the outer lamella, with long plumose 



