26o 



LEON J. COLE. 



around into the position in which they are normally carried, 

 that is, ahead of the lobster and pointing forward or even in- 

 ward. As a result the dactyl comes to lie on the side toward 

 the median plane, or even directed posteriorly. The primary 

 claw in Figs, i and 2 has nearly the normal position, but as will 

 be pointed out below, the torsion and bending are less than is 

 usual. Emmel (1907, p. 140) has emphasized the importance 

 of taking into account the normal torsion in considering the re- 

 lations of supernumerary parts in abnormal chelipeds. 



Fig. 6. Diagram showing the spacial relations and secondary symmetry in 

 the abnormal cheliped (full outlines). The dotted outlines show the theoretical 

 relations these parts should have in accordance with the "rules of secondary sym- 

 metry," leaving torsion out of account. 



In Fig. 6, by a similar diagram, are represented the conditions, 

 as regards rotation, of the three claws of the abnormal specimen. 

 As before, the appendage is considered as being extended straight 

 out laterally from the body. It will be noted that as a result 

 of the abnormal outgrowth the primary claw {IL, DL) has ro- 

 tated only about 45° from the vertical plane instead of nearly 

 90° as in the normal (Fig. 5). The amount of torsion in the 

 abnormal chelae will be discussed below with the consideration 

 of the relations of right and left. It may be said here, that as 



