MUSTELUS L.^VTS. 139 



In my 55 mm. embi'yo this cerebral brancli of the peri- 

 orbital sinus traverses the skull and then runs forward, as a 

 large vessel, along the lateral surface of the brain, between 

 it and the skull. Mr. Nomura here found a foramen in the 

 embryo he dissected. 



Review and Comparison of Eye Muscles. 



Corning (14), in his recently published and excellent work 

 on the eye-muscles and their innervation in the several 

 classes of vertebrates, to which reference has already several 

 times been made, comes to the conclusion expressed in tlie 

 following sentence: — ''Ichhalte also ander Homologie dervom 

 Oculomotorius innervirten Muskeln fest." This is directly 

 opposed to my own published opinion regarding these 

 muscles (3), and I cannot see that Corning in any way satis- 

 factorily explains the rather troublesome facts that I brought 

 forward in support of it. He is obliged, in fact, in order to 

 establish his proposition, to make certain assumptions that 

 have less support in fact than my assumptions had. To 

 explain the unusual innervation of the rectus inferior in 

 Petromyzon, by a branch of the abducens, he assumes that 

 the fibres destined to that muscle become detached from the 

 oculomotorius and attached to the abducens, intra-cranially. 

 And yet, although this interchange of fibres must surely be 

 extra- and not intra-cerebral, he did not establish it in the 

 specimen he examined, and it is in no way indicated in any 

 of the numerous works on the fish. To explain the important 

 differences in the innervation of the rectus internus, by a 

 branch of the superior division of the oculomotorius in certain 

 classes of vertebrates, and by a branch of the inferior 

 division of the same nerve in others, Corning assumes that it 

 would be sufficient, in order to produce the arrangement 

 found in the ones, for the opticus and oculomotorius of the 

 others to change slightly, at their exits from the cranium, 

 their relations to the recti muscles. Here he wholly over- 

 looks the very important fact that, in any such shifting 

 about of the points of exit of the two nerves in question, that 



