NATURAL HISTORY OF AMERICAN LOBSTER. 339 



toward the close of this period they become more sluggish, as if already affected by those 

 profound changes which at the next molt deprive them of their rowing organs and start 

 them upon a new career. Upon the bottom, however, the third-stage lobster is nearly 

 as helpless as at an earlier period, and while it may make the attempt to steady itself 

 upon its legs, it can not long maintain an upright position. Its future balancing organs 



Fig. 42. — Third larva, or third swimniing stage of the lobster, drawn to a scale reduced from that of figures 34 

 and 41. See legend of figure 34. Length 11. i mm., or 0.44 inch. 



are still in an undeveloped state. The swimmerets are now fringed with short rudi- 

 mentary setas, but do not come into full play until after the next molt. 



As Hadley has pointed out, at birth the larval appendages are less concentrated in 

 the head region than in the adult state, and this is most noticeable in the maxillipeds, 

 the exopodites of the third pair of which are used for swimming. From the first stage 

 62399°—" 13 



