278 NERVE COMPONENTS OF BONY FISHES. 



exhibits the " olfactory buds " of Blaue, which are so 

 general among the teleosts. The development, however, 

 shows that these are not survivals of a more primitive 

 condition, but that they are late and secondary acqui- 

 sitions. Blaue's supposition that they are related to the 

 lateral line organs or terminal buds is impossible for 

 several reasons. 



6. — I would reiterate the position taken by most of the 

 recent students of nerves, that the morphological value of 

 a given nerve is to be determined primarily by its terminal 

 relations, i. <?., its central nucleus and its peripheral end- 

 organ. These appear to be very constant, while its inter- 

 mediate course may be modified by so many cenogenetic 

 factors as to be of relatively small value in determining 

 the homologies. 



7. — Finally, I would urge that the significance of the 

 sensory components of the cranial nerves for metamerism 

 has been greatly misunderstood. The consequences 

 following the attempt to compare all sensory cranial 

 nerves directly with dorsal spinal roots and to apply Bell's 

 law in its simplest form to the cranial nerves have been 

 so disastrous to sound morphology that the tendency 

 among the most recent writers seems to be to deny the 

 metameric value of the sensory cranial roots altogether 

 and to confine attention to the motor roots. This is also 

 too extreme. The problems of metamerism in the case 

 of the sensory roots are vastly more complicated than in 

 the case of the motor ; yet I do not believe that they are 

 insoluble. Some suggestions as to the lines along which I 

 think the solution is to be sought are given in the 

 preceding section. 



December 31, 1S98. 



