S. I. Smith — Early stages of the Lobster. 5 



hairs. The last segment is relatively smaller and more quad- 

 rangular in outline, and the spines of the posterior margin are 

 much smaller. 



Fourth Stage. — In the next stage observed, the animal, about 

 three fifths of an inch (14 to 17 mm ) long, has lost all its schizo- 

 podal characters, and has assumed the more important features 

 of the adult lobster. It still retains, however, the free-swimming 

 habit of the true larval forms, and was frequently 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 an 

 adult form, it would undoubtedly be regarded as a distinct 

 genus. The rostrum is bifid at tip, and armed with three or 

 four teeth on each side toward the base, and in some specimens 

 with a minute additional spine, on one or both sides, close to the 

 tip. The fiagella of the antennulse extend scarcely beyond the 

 tip of the rostrum. The antennal scale is very much reduced 

 in size, but is still conspicuous and furnished with long plumose 

 hairs along the inner margin, while the flagellum is as long as 

 the carapax. The palpi of the mandibles have assumed the 

 adult character, but the mandibles themselves have not acquired 

 the massive molar character which they have in the older ani- 

 mal. The other mouth organs have nearly the adult form. 

 The anterior legs, although quite large, are still slender and 

 just alike on the two sides, while all the thoracic legs retain a 

 distinct process in place of the swimming exopodi of the larva. 



The lateral angles of the second to the fifth abdominal seg- 

 ments are prolonged downward into long spiniform teeth, the 

 appendages of these segments are proportionately much longer 

 than in the adult, and the margins of their terminal lamellae are 

 furnished with very long plumose hairs. The lamellae of the 

 appendages of the penultimate segment are oval, and margined 

 with long plumose hairs. The terminal segment is nearly 

 quadrangular, as wide at the extremity as at the base, the pos- 

 terior margin arcuate, but not extending beyond the prominent 

 lateral angles, and furnished with hairs like those on the 

 margins of the lamellae of the appendages of the penultimate 

 segment. 



In this last stage, the young lobsters swim very rapidly by 

 means of the abdominal legs, and dart backward, when disturbed, 

 with the caudal appendages, frequently jumping out of the water 

 in this way like shrimp, which their movements in the water 

 much resemble. They appear to be truly surface animals as in 

 the earlier stages. 



From the dates at which the different forms were taken, it is 

 probable that they pass through all the stages here described in 

 the course of a single season. How late the young, after reach- 

 ing the lobster-like form, retain their free-swimming habit was 

 not ascertained. 



