126 H. V. NEAL 



culature has been held on anatomical grounds by Bell ('30), 

 Stannius ('49), Huxley ('74, '75), Schneider (79), Gaskell ('86, 

 '89), Strong ('90), Fiirbringer ('97), Wiedersheira ('98), Gaupp 

 ('99), Kappers ('10) and on embryological grounds by Van Wijhe 

 ('82), Beard ('85), His ('88), Dohrn ('88, '90), Martin ('90), 

 Oppel ('90), Zimmermann ('91), Miss Piatt ('91), Hatschek ('92), 

 Hoffmann ('94-'00), von Kupffer ('94), von Kolliker ('96), Neal 

 ('96, '98), Sewertzoff '('98, '99), Carpenter ('06), Koltzoff COl), 

 Filatoff ('07), Belogolowy ('08, '10). 



Relatively few morphologists have regarded the abducens as 

 a splanchnic motor nerve. These are Stannius ('51) and Lan- 

 gerhans ('73) on the basis of the resemblance of the histological 

 structure of the posterior rectus mucle to visceral musculature 

 and Balfour ('78), Marshall ('81), Dohrn ('85) and Von Kupffer 

 ('94) on embryological grounds. 



Therefore on the basis of the strong preponderance of morpho- 

 logical opinion and on the ground that in its histogenesis, in its 

 relations to a somatic motor nidulus and to somitic musculature, 

 and finally in its histological structure the abducens resembles 

 a somatic motor nerve no alternative view of its morphology seems 

 possible. In its two divergent characters, namely, its lack of 

 connections with sensory and sympathetic ganglia, the abducens 

 shows primitive features which do not affect our conception of 

 its morphology. 



If, on the basis of the considerations presented above, there 

 seem good reasons for thinking that the pre-otic and post-otic 

 regions of the head were primitively alike and segmented in cor- 

 respondence with a somitic musculature, the question naturally 

 arises whether the eye muscle nerves and their relations throw 

 any light upon the vexed question of the number of cephalic 

 segments. The demonstration of a segmented somitic muscula- 

 ture with associated somatic motor nerves in the head region 

 would seem to warrant an optimistic view of the possibility of 

 a definite answer to the problem with which morphology has 

 wrestled without cessation for over a century. We may there- 

 fore turn to the following question: 



