S. T. Smith — JEarly Stages of the American Lobster. 375 



From the dates on which the different forms were taken, and from 

 the known rapidity with whicli tlie yonng of allied genera increase in 

 size and come to the mature form, there can be no donbt that the 

 young pass through all the stages I have described in the course of a 

 single season, and it is probable that the largest of the young just 

 mentioned had not been hatched from the egg more than six weeks 

 and very likely only a much shorter time. How long the young- 

 retain their free- swimming habit after arriving at the lobster-like form, 

 was not ascertained. 



Specimens three inches in length have acquired nearly all the char- 

 acters of the full grown adult. The rostrum is not more than a 

 fourth of the length of the carapax including the rostrum, and in 

 form is more like that of the second and third stages of the larvae 

 than that of the earliest stage of the adult form. It is regularly and 

 very narrowly triangular, the terminal third slender, spiniform and 

 unarmed as seen from above, but broader as seen in a lateral view and 

 armed below with two small teeth directed forward, the middle por- 

 tion armed each side above with two spiniform teeth, the posterior 

 one slightly the smaller, and sometimes a third, still smaller one, 

 back of the others. 



The antennulfe are about two-thirds as long as the carapax includ- 

 ing the rostrum, the peduncles reach nearly to tip of the rostrum, 

 and the inner llagella are slightly longer than the outer. The flagella 

 of the antennae are nearly as long as the rest of the animal, and the 

 peduncle reaches nearly to the tip of the rostrum. The antennal 

 scale is still considerably larger proportionally than in the full grown 

 adult, reaching nearly to the extremity of the peduncle, but it is 

 reduced to a stout tooth-like appendage with a lamellar expansion 

 upon the inner side. 



The mandibles are nearly as massive as in the full-grown adult, and 

 the posterior portion of the outer edges of the crowns are smooth and 

 continuous and not dentate, as in the earlier stages. 



The anterior cephalothoracic legs are relatively very mucli stouter 

 than in the earlier stages and are unlike on the two sides, as in the 

 fall-grown, the propodus upon one side being much broader than 

 upon the other and the prehensile edges of the projDodus and dactylus 

 wanting the dense clothing of short hairs or seta; which are conspicu- 

 ous upon the other leg. 



The sexual appendages upon the first segment of the abdomen are 

 fully developed. The sides of all the abdominal segments, the telson, 

 and the appendages are almost exactly as in the full-grown. 



