No. 3-] THE VERTEBRATE HEAD. 50I 



In glancing over the views regarding cranial anatomy that 

 have been held since the beginning of this century, we find a 

 suggestive hint in the shift of opinion, as to the decidedly rela- 

 tive nature of all our views on morphological problems. There 

 has been a distinct rise in the point of view, but scarcely any 

 of the earlier problems are yet solved ; new ones have been 

 added, but those that have been handed down have grown 

 broader and increased in proportions as a mountain on nearer 

 approach. There has been a gradual change in front, keeping 

 pace with the advance of our knowledge and with the changes 

 in our methods of interpretation. During that period the very 

 soul has been breathed into the body of comparative morphol- 

 ogy, and as a result, our interpretations are directed towards 

 explaining anatomical structures in connection with their past 

 development. 



At the beginning of this century, on account of superficial 

 appearances, the conception took rise that the head is divided 

 into definite segments. The obvious division of the skull by 

 sutures was gradually worked into the theory that the cranium 

 represents a number of modified vertebrae ; and then began on 

 the part of anatomists, the efforts to determine the number of 

 these segments or vertebrae in the skull. Oken and Goethe 

 formulated the theory which was taken up by that eminent 

 anatomist Richard Owen, who lavished upon it an amount of 

 attention and labor that was worthy of a more substantial 

 theory, but the mistakes of that great man have proved of 

 benefit to other morphologists. 



This was the beginning of the idea that the head region rep- 

 resents a definite number of segments. Originally founded on 

 external features of no segmental importance whatsoever, and 

 not essential to the question which they served to introduce, 

 the problem gradually widened and deepened and reached the 

 essential parts connected with this segmental condition. The 

 first conspicuous change of front came with the delivering of 



species of Elasmobranchii. I collected material (Galeus canis and Squalus 

 acanthias) for that purpose, and began studies along that line, but, finding new 

 and undescribed conditions in the head region, my attention was gradually drawn 

 off from the original purpose and directed towards cranial anatomy. 



