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MR. W. BATESON ON ABNORMAL 



[June 17, 



parts appear to be normal with the exception of the third maxiUi- 

 pede of the right side. This structure, however, has the form 

 shown in fig. 1, A, differing entirely from the ordinary condition 

 of the appendage. Fig. 1, B, is taken from the third maxillipede 

 of the left side and shows the ordinary structure of the same parts. 

 On comparing the two figures, it will be seen that the protopodite 

 does not differ in the limbs of the two sides ; that the exopodite of 

 the right side is essentially like that of the left, but that it lacks 

 the inner process and the flagellum which are borne by the normal 

 part. There was some indication that this branch of the limb had 

 been injured, and perhaps the tlagollum may have been torn away, 

 but the appearances were not such as to warrant a conclusion on 

 this point. The branchial epipoditcs (not shown in the figures) were 

 normal in both cases. The endopodite of the right side was entirely 



A represents the abnormal third maxillipede of the right side. B shows the 

 same pai-ts on the left side, which are normal. 



bp, protopoclite : ep, epipodite ; dp, dactylopodito ; -pp, pi-opodite ; cp, carpo- 

 podite ; mi, meropodite and ischio]iodite ankylosed together, g indicates 

 the line of their separation ; g' corresponds to the groove at which a 

 chela can be thrown off. 



peculiar and was, in fact, literally transmuted into the likeness of 

 one of the great chelae. It consists of a single joint (mi), articulating 

 with the protopodite centrally and bearing the carpopodite. This 

 single joint represents, as it were, the ischiopodite and meropodite 

 of an ordinary chela, but these two parts are ankylosed together, 

 and the articulation between them is only represented by a groove 

 (r/) ; another groove (</') represents the groove upon the ischiopodite 

 of the chela at which the limb is commonly thrown off by the 

 animal if it is injured. The carpopodite, propodite, and dactylo- 

 podite are feebly movable on each other and hardly differ, save in 

 absolute size, from those of the normal chela. The shape, propor- 

 tions, and texture are all those of the chela. 



Cases like the foregoing, of the complete transformation of a part 

 into the likeness of another part, though very common among 



