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which we assume will not be doubted, then we must con- 

 clude that we have, in this clearly monophyletic group, a 

 genuine case of fin migration, since the pelvic fin of 

 Teleosts may be either abdominal, at the side of the anus, 

 thoracic, just behind the pectoral fin, or jugular, in front 

 of the pectoral. Further the fin must have moved from 

 behind forwards, since it may be clearly deduced from the 

 fossil forms that the abdominal position is unquestionably 

 more primitive than the jugular. iVow in Elasmobranch 

 fishes, according to Gegenbaur's hypothesis, the pelvic fin, 

 having been formed from the branchial skeleton, must 

 have migrated from before backwards, unless the addi- 

 tional hypothesis of the extension of the branchial region 

 further back than we have any knowledge, is evoked. t It 

 must be noted at once, first, that all palseontological evi- 

 dence is against such an assumption, and second, that this 

 migration, if it occurred at all, must have taken place at 

 a remote geological period. On the other hand, the 

 migration of the pelvic fin of the Teleost is not only some- 

 thing more than an hypothesis, but it must also have 

 occurred within comparatively recent times. Now several 

 attempts have been made to deduce the migration of the 

 Elasmobranch fin from its innervation, and so far the 

 Teleosts have been ignored, in spite of the fact that here 

 we might with much more reason expect to encounter 

 such evidence. Unfortunately, however, in the latter 

 group, the jugular pelvic, as in the case of the Plaice, is 

 supplied b}^ the anterior spinal nerves of its region, and 

 the abdominal pielvic, as in the several fishes investigated 

 by Stannius, is supplied by the posterior nerves of its 



t It may, of course, be maintained, as it is in the case of soine Elasmo- 

 branchs, that the pelvic fin of Teleosts migrated first backwards and then 

 forwards. We have ignored the former possibility (which after all would 

 be purely hypothetical), in order to concentrate attention on the latter, 

 where the migration theory may be the more satisfactorily tested. 



