REPORT OF COMMISSI/DNERS OF INLAND FISHERIES. 231 



EXPLANATION OF PLATE 32. 



Fourth stage; length. 14.3 mm.; age, 14 days. The greatest change in form which 

 takes place {at any one molt) in the life of the lobster occurs in tlie transition 

 from the third to the fourth stage. 



First antenn.e: 



Both exopodites and endopodites are much elongated, and the segments 

 are more distinct than in any previous stage; the olfactory setae are 

 very distinct. 



Second antenn.e: 



The endopodites have, in a single molt, extended into long whip-like 

 lashes, distinctly segmented and nearly two-thirds as long as the body; 

 there has been no further development in the exopodites. 



Eyes: 



These are relatively much smaller than in the previous stages. 



Maxillipeds: 



These still retain the exopodites and they remain functional., 



Chelipeds: 



These resemble more fully than in any previous stage the adult claw; 

 right and left are similar; since the second stage a torsion has taken 

 place (affecting, as Herrick has shown, the carpopodite or fifth joint) 

 so that in the present position of the claw the dactyl opens inward; the 

 exopodites have been lost in the recent molt. 



Ambulatory appendages: 



These have lost, in the recent molt, the exopodites which, as is also the 

 case in the chelipeds, have atrophied to functionless stvunps (not 

 shown in the drawing) ; no torsion has taken place in the first two pairs 

 (the second and third chelate limbs), and the dactyls of the claws open 

 upward and outward as before. 



Abdominal appendages: 



These have become fringed with a border of delicate setae; the exopodites 

 and endopodites of each are clearly distinct and, for the first time, 

 functional; the appendages of the last abdominal segment have increased 

 in size and are now bordered by a fringe of long matted setse; the ap- 

 pendages of the first segment have not appeared at this stage. 



Tail: 



Owing to the changes in the appendages of the last abdominal segment, 

 the tail now closely resembles that of the adult lobster. 



