98 H. V. NEAL 



The study of histogenesis has shown that connection between 

 muscle and nerve is not primary but secondary. This suggests 

 the possibihty that new segmental relations may be acquired 

 by somatic motor nerves and that a nerve may invade territory 

 foreign to it. In this way some peculiarities in the relations of 

 eye-muscle nerves may be explained. 



RELATIONSHIPS OF THE EYE MUSCLE NERVES 



1. Is the musculature innervated by the eye-muscle nerves somitic 



musculature? 



The eye-muscle nerves innervate muscles derived from Van 

 Wijhe's first, second and third somites. The oculomotor inner- 

 vates muscles differentiated from the first, the trochlear inner- 

 vates that derived from the second, and the abducens is con- 

 nected with a muscle formed from the third and a part of the 

 second (Dohrn '07) . Are these muscles serially homologous with 

 those innervated by spinal somatic motor nerves? This obvi- 

 ously depends upon the somitic nature of Van Wijhe's three 

 'somites.' 



They have been regarded as true somites by many morphol- 

 ogists including Van Wijhe ('82), Oppel ('90), Miss Piatt ('91, 

 '97), Hoffmann ('94), Neal ('96, '98), Furbringer ('97), Kolt- 

 zoff ('01), Killian ('91), Boecke ('04), FilatofT ('07) and their pres- 

 ence has been demonstrated in such diverse groups as Selachii 

 (Van Wijhe '82, Miss Piatt '91, Hoffmann '94, Neal '96, Braus 

 '99, Johnston '09); Cyclostomes (Koltzoff '01); Teleosts (Boecke 

 '04) ; Amphibia (Miss Piatt '97) ; and Reptiles (Oppel '90, Fila- 

 toff '07). 



On the other hand the eye muscles have been regarded as 

 splanchnic muscles by Stannius ('51), Langerhans ('73), Balfour 

 ('78), Marshall ('81, '82), Dohrn ('85, '87, '04, '07), Houssay 

 ('90), Hatschek ('92), Rex ('97, '05) and Sewertzoff ('98), and 

 the presence of true somites in the pre-otic region has been 

 denied by Kastschenko ('88), Rabl ('92) and McMurrich ('12). 

 Sewertzoff ('98 b) bases his objection to the inclusion of the 

 second myotome in the series of somitic muscles upon the con- 



