S. I. Smith — Early stages of the Lobster. 3 



longer than the external maxillipeds. The pecliform branch is, 

 however, somewhat stouter than in the outer legs, and subcheli- 

 form. The legs of the second and third pairs (fig. D) are simi- 

 lar to the first but not as stout. The legs of the fourth and 

 fifth pairs are still more slender, and styliform at the extremity 

 as in the adult. 



The exopodal branches of all the legs and of the external max- 

 illipeds are quite similar, and differ very little in size. In life, 

 while the animal is poised at rest in the water, they are carried 

 horizontally, as represented in figure B, or are curved up over the 

 carapax, sometimes so as almost to cover it. The blood circu- 

 lates rapidly in these appendages, and they undoubtedly serve, 

 to a certain extent, as respiratory organs, as well as for locomo- 

 tion. By careful examination, small processes were found rep- 

 resenting the normal number of branchiae to each leg.* These 

 rudimentary branchiae, however, differ somewhat in different 

 specimens, being very small, and scarcely distinguishable, in 

 what appear to be younger individuals, from the rudimentary 

 epipodi, while in others, apparently older, they are farther 

 developed, being larger, more cellular in structure than the 

 epipodi, and even showing an approach to crenulation in the 

 margins, as in figure D. 



The abdomen is slender, the second to the fifth segments 

 each armed with a large dorsal spine curved backward, and with 

 the lateral angles produced into long spines, and the sixth 

 segment with two dorsal spines. The proportional size and the 

 outline of the last segment is shown in figure B ; its posterior 

 margin is armed with a long and stout central spine, and each 

 side with fourteen or fifteen plumose spines or setae, which are 

 articulated to the margin. 



Second Stage. — In the next stage the larvae have increased 

 somewhat in size, and the abdominal legs of the second to the 

 fifth segments have appeared. The rostrum is much broader, 

 and there are several teeth along the edges. The basal segments 

 of the antennulas have become defined, and the secondary flagel- 

 lum has appeared but is not subdivided into segments. The 

 antennas and mouth organs have undergone but slight changes. 

 The first thoracic legs are proportionately larger and stouter 



* The number of branchiae, or branchial pyramids, in the American lobster is 

 twenty on each side : a single small one upon the second maxilliped, three well- 

 developed ones upon the external maxilliped, three upon the first thoracic leg, four 

 each upon the second, third and fourth, and one upon the fifth. This number is 

 perhaps different in the European species. De Haan (Fauna Japonica, Crustacea, 

 p. 146) gives the number, for the genus Homarus, as nineteen on each side, giving 

 only two for the external maxilliped, while Owen (Lectures on the Anatomy of the 

 Invertebrate Animals. 2d ed., p. 322) and Edwards (Hist. nat. des Crust., i, 86) 

 give the whole number on each side as twenty-two, although Edwards in the 

 second volume of the same work, under Homarus, p. 333, gives twenty as the 

 number. 



