236 NERVE COMPONENTS OF BONY FISHES. 



dorsal edge of the rectus inferior and within that muscle 

 divides, some fibres remaining within the muscle and 

 others emerging on the cephalic and ventral side of it. 

 The latter soon separate from the muscle and continue 

 cephalad. A branch is given off which runs dorsad to 

 supply the rectus internus and the remainder runs far for- 

 ward to supply the obliquus inferior. 



The oculomotorius, then, runs under the m. rectus 

 superior, the r. ophthalmicus and the n. opticus. It crosses 

 the m. rectus internus dorsally near its origin, but lies far 

 ventrad of that muscle when the main nerve for it is 

 given off. It pierces the dorsal portion of the m. rectus 

 inferior and enters the obliquus inferior from its dorsal 

 side. 



Now, it is obvious that this arrangement in Amblystoma 

 conforms to the scheme which Allis gives for the Anura, 

 rather than the one for the Urodela. The lack of uni- 

 formity of my results with his scheme, both in the fishes 

 and the Amphibia, together with the fact that his diagrams 

 do not in all cases correspond with his authorities (e. g. , 

 in the diagram of the Cyclostomata, based on Flirbringer, 

 the nerve to the m. rectus superior is drawn over the 

 ophthalmicus profundus, while Flirbringer says that it 

 runs below that nerve) suggest that his entire phylo- 

 genetic scheme should be received with some reserve. 



Again, to say nothing of the acknowledged incomplete- 

 ness and possible inaccuracy of the data upon which the 

 table is constructed, it seems rash to construct even a 

 tentative phylogenetic tree upon a single character of this 

 sort. But, aside from this, unless one were to apply the 

 neuro-muscular theory rigidly in the ontogeny (which few 

 morphologists now-a-days are willing to do) it is difficult 

 to see why so exaggerated importance should be given to 

 the relative positions of these nerves and muscles. There 

 is no sufficient evidence that these nerves have been split 

 off from the skin, as Allis assumes that most of the cranial 

 nerves have been (a point to which we shall recur), but 

 on the other hand, the best recent work on this subject 

 {e. g. Dixon, '96 and Neal, '98) adds very emphatic testi- 



