148 PROFESSOR MARSHALL. 



the recent observations of Wiedersheim 1 on the nervous system of 

 Lepidosiren (Protopterus) annectens. Wiedersheim describes a mode- 

 rately long but exceedingly slender nerve which leaves the skull 

 through a special foramen in front of that of the fifth, and loses itself 

 in the eye-muscles in a manner which he was unable to determine with 

 certainty. In spite, however, of taking "all conceivable pains," he was 

 unable to ascertain whether this hitherto overlooked eye-muscle nerve 

 arises independently from the brain, or is a mere branch of the fifth, 

 though he is inclined himself to regard it as an independently arising 

 third nerve. 



Under these circumstances, and especially when we consider Wieder- 

 sheim's discovery of a distinct eye-muscle nerve, and his statement of 

 the extreme difficulty he experienced in tracing this nerve even to the 

 limited extent which he succeeded in doing, we must, I think, con- 

 clude that, whatever subsequent investigation may tell us, Lepidosiren 

 at present offers no definite or reliable evidence against the statement 

 that the eye-muscle nerves are independently arising nerves in all 

 vertebrates in which the eye-muscles themselves are present. 



6. Amphibia. — Statements of exceptional innervation of one or more 

 of the eye-muscles among Amphibia are by no means uncommon ; and 

 though I have devoted some time to making my list as complete as 

 possible, I am far from certain that I have succeeded in collecting all 

 the alleged cases. The following list includes all I have been able to 

 refer to, and certainly all that are mentioned in the standard works 

 and papers on the subject : — 



A. Apoda (Gymnophiona). — Wiedersheim, in his monograph on this 

 group, 2 mentions that in Coecilia the eye-muscles are present, but of 

 exceedingly small size, so small indeed that he could not make out 

 either their number or arrangement ; neither was he able to ascertain 

 anything concerning their innervation ; indeed, he makes no mention 

 whatever of the eye-muscle nerves. Fischer 8 also failed, from his dis- 

 section of a single specimen, to make out anything definite concerning 

 the eye-muscle nerves. Inasmuch as the eyes of Coecilia are very 

 small, it would seem probable that we have here another instance of 

 rudimentary eyes, accompanied very possibly by a reduction in the 

 number of eye-muscles ; and we have already seen that the evidence 



1 Wiedersheim, Morphologische Studien, Heft 1 ; III. Das Skelet und Nervensyntem von 

 Lepidosiren annectens, 1880. 



a Wiedersheim, Die AnaUmie der Gymnopkionen. Jena, 1879, pp. 55, 56, and 61. 

 3 Fischer, op. cit., p. 47. 



