REPORT OF COMMISSIONERS OF INLAND FISHERIES. 117 



small dimensions. The irregular form at this region (Fig. 17, a) is 

 partially the effect of the injury received during its development. 

 Just distal to this irregular region is a rudimentary joint? (j). It is 

 indeed rather badly deformed, but it still presents the characteristics 

 of a joint between the carpopodite and the next distal segment. I 

 watched the live lobster to see whether it had any ability to move 

 this abnormal claw. Occasionally there was a display of activity in 

 which the abnormal structure would be carried past the posterior 

 face of the normal propodite, so that its plane of motion would be at 

 an angle of approximately 45 degrees to the corresponding plane of 

 motion for the normal propodite. But it was very rarely that this 

 abnormal process was seen to function in this manner, and, indeed, 

 this might be expected in view of the severe injuries which the muscu- 

 lature at its base sustained during development. 



' Farther distally, i. e., beyond the joint just described, this abnormal 

 structure enlarges again and finally terminates distally in three large 

 prongs. Figure 17, 1'R', I'W, and D'(R+L). Upon closes examina- 

 tion it becomes evident that IR and IL represent tw^o extra indices. 

 They diverge from each other at an angle of about 45 degrees. The 

 dorsal border of each index is dentated with a row of serrated teeth 

 (Fig. 18, T); the tips are capped with the usual horny points; neither 

 prong has any indication of a joint, and their morphological con- 

 tinuity with the propodite is most clearly evinced by a row of hair 

 on the ventral surface of each index (Fig. 17, h, h') : These two 

 row^s of hair begin at the distal extremity of each index, continue 

 proximally along the ventral surfaces in two distinct linear series, 

 and extend down almost the entire length of the abnormal propodite. 

 The third prong D'(R+L) is even more interesting; for while 

 at first glance it may appear single, it is evidently morphologically 

 a double dactyl. It takes its origin from the dorsal surface of the 

 propodite, near the angle at the base of the two indices; and pro- 

 jects upwards at right angles to this pair of indices. Near the base 

 is a constriction (Fig. 18, j) w^hich may be interpreted as a rudi- 

 mentary joint, although I was unable to observe that it was func- 



