82 E. A. ANDREWS. 



it morphologically would seem to meet with more difficulty in 

 assuming it to represent a claw than in assuming it to represent 

 two fused dactyls or a branched dactyl. Were it a claw with 

 fused articulation of dactyl and index we would have a limb so 

 doubled distally as to have an extra segment and a lack of coin- 

 cidence between the two series of segments. A propodite would 

 spring from propodite instead of from a carpodite ; and if we 

 bear in mind the partial double appearance of the propodite and 

 regard it as a fusion we would have a carpodite and a propodite 

 springing from a carpodite, and so on. 



Bateson's thorough study led to the conclusion that almost all 

 cases could be interpreted as repetitions of claws in which there 

 was more or less suppression of index or of carpus. The 

 pronged structure would then be regarded as two party fused 

 dactyls placed face to face and we would expect to find some 

 representative of the two indices. On the line of imagined fusion 

 there is a slight eversion of membrane where the pronged struc- 

 ture articulates with the propodite, but there is no reason for 

 regarding this as of any morphological significance. 



In the case described by Faxon, as quoted above, Bateson 

 thought he had found a representative of the required indices in 

 a small protuberance shown in Faxon's Fig. 2 ; this however 

 was an error for I am informed by Faxon that " the artist un- 

 fortunately represented a protuberance which does not exist." 



There are thus two cases in which pronged structures have 

 nothing with them to countenance the idea that they represent 

 double dactyls with even traces of double indices. Moreover, it 

 will be seen from the above Fig. 2 that the prong nearer to 

 the dactyl is not a mirror image of that dactyl but that it rep- 

 resents the index and likewise the other prong is not a mirror 

 image of the index but represents the dactyl ; this is true since 

 all have their serrations nearer to the posterior face than to the 

 anterior face. There is thus a departure from Bateson's rule of 

 symmetry and we have to deal with a very unusual abnormality 

 that is not interpretable in the same way as most of those hitherto 

 known. 



But any morphological interpretation seems somewhat prema- 

 ture and unsatisfactory in the lack of more knowledge of the 



