INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 527 



Specimens in this stage were taken only twice, July 1 and 15. They 

 have the same habits and general appearance as in the first stagfi, but 

 are readily distinguished by the possession of rudimentary abdominal 

 legs. In color they are almost exactly the same, only the orange-colored 

 markings are perhaps a little less intense. 



Tliird stage. — In the third stage (Plate IX, figs. F, F, G,) the larvae 

 are about half an inch (12 to 13 mm ) in length, and the integument is of a 

 much firmer consistency than in the earlier stages. The antennulse are 

 still rudimentary, and considerably shorter than the rostrum, although 

 the secondary flagellum has increased in length, and begins to show 

 division into numerous segments. The antennoe 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, maxillse, and first and second inaxillipeds have changed 

 very little, although in the second maxillipeds the extremity of the ex- 

 ognathus begins to assume a flagelliform character, and the branchiais 

 represeuted by a small process upon the side of the epignathus. The 

 external maxillipeds 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 exopo- 

 dal branches of all the legs, as well as of the external maxillipeds, are 

 relatively much smaller and more unimportant. The epipodi (fig. G) 

 are furnished with hairs along the edges, and begin to assume the char- 

 acters of these appendages in the adult. The branchiae (fig. G) have 

 developed rapidly, and have a single series of well-marked lobes along 

 each side. The abdomen still has the spines characteristic of the ear- 

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

 dages of the second to the fifth segments have become conspicuous, their 

 lamellae have more than doubled in length, and the margins of the ter- 

 minal half are furnished with very short ciliated setse. The appendages 

 of the penultimate segment (fig. F) are well developed, although quite 

 different from those in the adult. The outer lamella wants wholly the 

 transverse articulation near its extremity, and both are margined, ex- 

 cept the outer edge of the outer lamella, with long plumose hairs. The 

 last segment is relatively smaller and more quadrangular in outline, 

 and the spines of the posterior margin are much smaller. 



The only specimens procured in this stage were taken July 8 and 15. 

 In color they were less brilliant than in the earlier stages, the orange 

 markings being duller and whole animal slightly tinged with greenish 

 brown. . 



In the next stage observed, the animal, about three-fifths of an inch 

 (14 to 17 mm ) long, has lost all its schizopodal characters, and has assumed 

 the more important features of the adult lobster. It still retains, how- 

 ever, the free-swimming habit of .the true larval forms, and was fre- 

 quently taken at the surface, both in the towing and hand net. Although 

 resembling the adult in many features, it differs so much that, were it 



