370 S. I. Smith — Early Stages of the American Lobster. 



Early stages of the adult form. 



Between this stage and the thii'd larval stage there is possibly an 

 intermediate form wanting. The changes in the whole appearance of 

 the animal have been so much greater than between the first and 

 second or between the second and third larval stages, that, although 

 the diiference in size is inconsiderable, the whole change did not per- 

 haps take })lace at one molt. 



In this stage the animal is about three-fifths of an incli (14 to 17""") 

 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. Al- 

 thougli it resembles the adult in many features, it differs so much 

 that, were it an adult, it would undoubtedly be regarded as a distinct 

 genus. 



The carapax has nearly the same form as in the adidt, being longer 

 and pro})ortionally narrower than in the third larval stage, and not 

 gibbous upon the sides posteriorly. The areolation is as distinct as 

 in the adult. The tooth upon the anterior margin, just over the base 

 of the antenna, is rather more prominent than in the adult, but there 

 seems to be no small spine back of this on the side of tlie carapax as 

 there is in the adult. The rostrum (plate XY, figs. 4 and 5, enlarged 

 10 diameters) is abou.t two-fifths as long as the carapax including the 

 rostrum, broad, expanded in the middle, and terminates in a slender 

 bifid tip (fig. 4a, enlarged 25 diameters). The edges are clothed with 

 plumose seta? (fig. 4&, enlarged 50 diameters) and three or four teeth 

 on each side besides a small one near the base and a little way back 

 from the margin, and in some specimens with a minute additional 

 spine on each side near the slender terminal portion. 



The ocular peduncles are elongated and of nearly the same form as 

 in the adult. 



The antennulffi (plate XV, fig. 10, enlarged 20 diameters) have 

 assumed the form and character of those of the adult. The basal 

 segment is broad and has a well developed auditory chamber contain- 

 ing otolithes and similar to that of the adult, although, in the alco- 

 holic specimens examined, the chamber appeared to be open wliile in 

 the adult it is closed. All the segments of the peduncle have a few 

 hairs or seta? upon the outside, and the ultimate and penultimate on 

 the inside also. The flagella are nearly equal in length, the outer 

 being slightly longer, and extend only a little beyond the tip of the 

 rostrum. The outer flagellum is very stout, composed of ten to twelve 



