author's abstract of this p.vper issued 

 by the bibliographic service, jaxuart 16 



PRIJMARY NEUROMERES AND HEAD SEGMENTATION 



HORACE W. STUNKARD 



New York University 



TWENTY FIGURES 



The problem of the segmentation of the vertebrate head, old as 

 Oken and Goethe, has possibly attracted as much interest and 

 incited as much investigation as any other one question in 

 vertebrate morphology. The first investigators advanced a 

 theory based upon superficial external features the sutures of 

 the skull. Subsequent workers have investigated every struc- 

 ture enclosed within the skull, with the hope that light may be 

 thrown upon the obscurity and uncertainty enveloping the evolu- 

 tion of the head. This complex, intricate structure manifests 

 evidences of past ages; remnants and vestiges of the long period 

 of developmental history still persist, but the character of the 

 evidence, the complications, omissions, and reversals have 

 baffled all attempts at solution. 



Huxley ('58) overthrew the vertebral theory of the skull, 

 Balfour (78) introduced mesodermal head cavities as criteria of 

 segmentation and clues to the number and relationship of the 

 cephalic somites, and Gegenbaur ('87) added cranial nerves and 

 visceral arches as segmental criteria. Van Wijhe ('86), ('89) con- 

 sidered the dorsal ganglia of importance and formulated criteria 

 to determine the true segmental nerves. He regarded the 

 olfactory and optic nerves as parts of the brain and not of seg^ 

 mental value. 



Von Baer ('28) noticed symmetrical folds in the hindbrain of 

 the chick; Dohrn ('75) related them to the mesodermal somites, 

 and Beraneck ('84) to the cranial nerves. Balfour reported that 

 the first gives rise to the cerebellum, and considered it doubt- 

 ful whether the other constrictions have any morphological 



331 



JOURNAL OF MORPHOLOGY, VOL. 30, NO. 2 



