326 NOTES ON THE STRUCTURE AND RELATIONS 



fatigable friend Mr Robert Dick, of whom I may well say, 

 that he " has robbed himself to do me service." 



I trust the members of the Society will excuse minute- 

 ness of detail on a subject regarding which it is neces- 

 sary to be minute in order to be intelligible, and in which, 

 though I have to deal with the oldest of the vertebrate exist- 

 ences of whose mechanism we can know anything positive, 

 our knowledge is but in the forming, and still very incom- 

 plete. Permit me, ere I conclude, to refer at some length 

 to a subject closely connected with these organisms. I have 

 exhibited to the Society this evening certain remains of the 

 earliest ganoids that bear on two points which have already 

 drawn the attention of naturalists, and which, judging from 

 the recent writings of Agassiz, bid fair to attract their no- 

 tice yet further. In the jaws of Asterolepis you have seen 

 strongly-marked reptilian characteristics, which are exempli- 

 fied at the present time, though less amply, in the upper jaw 

 of the alligator, and in that of the most perfectly developed 

 of all recent fishes, — the ichthyic-reptilian Lepidosteus. Of 

 the vertebral mechanism of the Asterolepis there survive not 

 a trace ; but in that of its contemporary the Coccosteus you 

 have seen what is deemed a foetal peculiarity. The vertebrae 

 represented by but the blank space between the upper and 

 under apophyses were cartilaginous ; and it is held that in 

 all the other ganoids of the period the apophyses were as 

 cartilaginous as the vertebrae themselves, seeing that both 

 are equally represented in their fossil remains by but a blank. 

 And what is foetal peculiarity manifested in the immature in- 

 dividuals of one class or genus, is accepted in Agassiz's new 

 scheme of classification, when manifested in the mature ani- 

 mal of another class or genus, as a sign of inferiority. In 

 his " Principles of Zoology," published in 1848, we find him 

 exemplifying his scheme with great clearness and precision, 

 by the white fish (one of the Salmonidse of the American 



