68 SKELETON OF THE PAIRED FINS OF ELASMOBRANCHS. 



anal fins of ScyUium I find that their cartilaginous rays 

 develop at a considerable distance from, and quite inde- 

 pendently of, the neural and hsemal arches, and that they are 

 at an early stage of development distinctly in a more advanced 

 state of histological difi'erentiation than the neural and hsemal 

 arches of the same region. I have also found exactly the 

 same in the embryos of Lepidosteus. 



I have, in fact, no doubt that the skeleton of both the 

 paired and the unpaired fins of Elasmobranchs and Lepi- 

 dosteus is in its development independent of the axial 

 skeleton. The phylogenetic mode of origin of the skeleton 

 both of the paired and of the unpaired fins cannot, however, 

 be made out without further investigation. 



