264 LEON J. COLE. 



claws lack 3 5° of being turned as far as called for by the theoretical 

 positions (solid outlines, Fig. 7), to say nothing of the additional 

 80° which would be necessary for them to assume the positions 

 as a result of normal torsion (dotted outlines, Fig. 7). As a 

 matter of fact, this torsion should not be expected in the secondary 

 claws, since they divide from each other at a considerable distance 

 from the base, and the torsion of the propodite takes place en- 

 tirely, or practically so, at its base. Thera would be no torsion 

 in the basal part of the extra outgrowth, since in that region 

 which is potentially double, the tendencies to rotation in opposite 

 directions would neutralize each other. The divergence of the 

 primary claw being further proximal, that has been able to under- 

 go some rotation (45°) as already described. Now as to the 

 failure of the planes of the secondary claws to lie at right angles 

 to each other, as they should, according to Fig. 7, if torsion is 

 eliminated. This is probably to be accounted for upon mechani- 

 cal grounds, the union of the parts only a short distance proximad 

 interfering with and restricting the divergence of these planes. 

 If the double outgrowth had taken its origin upon a more basal 

 portion of the appendage, it is safe to assume that the planes of 

 the distal claws would have attained more nearly the theoretical 

 positions.^ 



The relations of secondary symmetry in the more proximal 

 parts of the appendage appear to be amenable to the same rules ; 

 but owing to the way in which the various parts are "com- 

 pounded" (to use Bateson's term) before they actually divide, 

 this exposition becomes extremely complicated and would serve 

 no useful purpose at this time, since the discussion given above 

 as to the relations of the claws has served to illustrate the factors 

 involved. This compounding accounts for the absence of large 

 spines along the dorsal side of the extra propodite, which has 

 already been mentioned. 



1 In Emmel's interesting "specimen No. 5" the extra chelae arose from the me- 

 ropodite, and he here found (the union being further proximad) that each of the 

 claws had undergone a full rotation, each in its normal direction of torsion. Accord- 

 ing to his description (Emmel, 1907, p. 141) the primary or normal claw had rotated 

 90°, but each of the extra claws had rotated i8o°! Why this should have been seems 

 difficult to understand and Emmel offers no explanation. Why, with the direction 

 of torsion opposed in contiguous claws, its amount should be limited to less than 

 90°, as in the specimen here described, is obvious; but why in any case it should 

 be greater than 90° seems inexplicable. 



