REPORT OF COMMISSIONERS OF INLAND FISHERIES. 75 



6. The exopodites of the thoracic appendages are still functional. 



7. The swimmerets of the abdomen have each developed a 

 delicate fringe of setae. 



8. The last segment of the abdomen has given out on each side 

 an appendage consisting of an exopodite and an endopodite, these 

 fringed with setae. The appearance of the "tail" has been greatly 

 modified since the previous stage. 



9. The average length of the third stage is 11 mm. 



Fourth Stage. 



The changes which occur between the third and fourth stage are 

 the most distinct of any which take place in the life history of the 

 lobster, and are as follows: 



1. The body undergoes a straightening and elongation. 



2. In the first antennae the two branches of each appear equal in 

 length, definitely segmented and bordered with setae. 



3. The second antennae (the endopodites) emerge as long, seg- 

 mented, whip-like structures which now, because of the prominence 

 of the basal joints, can be folded back along the side of the body. 



4. The thoracic appendages have again shifted forward, this 

 time to adult position. Moreover, they have lost, with the exception 

 of the maxillepeds, the swimming branches (exopodites). Rudi- 

 ments of these are evident, however, as small functionless stumps 

 with no sign of setae on the ischium or third joint of the chelae and 

 ambulatory appendages. 



5. The appendages on the under side of the abdomen have become 

 larger and stronger and fringed with a heavy border of setae. They 

 become highly functional in this stage. 



6. The exopodites and endopodites arising from the last ab- 

 dominal segment and forming with the telson the "tail-fan" have 

 developed in size and now are equal in length to the telson itself. 

 They too are fringed with a heavy border of long setae. 



