

BRANCHIAL SENSE ORGANS OF ICHTHYOPSIDA. 197 



the oral raucous membrane, which stretched towards the nasal groove, 

 but which later in the development disappeared. Smelling, argued 

 Marshall, is only a modified breathing, and thus no violent physio- 

 logical change is necessary to convert a gill into a smelling organ. 



Wiedersheim 1 himself formerly supported Marshall's view, and 

 pointed out that in Epicrium, and probably in other Gymnophiona as 

 well, there are on either side two olfactory nerves, one dorsal and one 

 ventral, the roots of the two being perfectly independent and some little 

 distance apart. He considered these roots to be homologous with the 

 dorsal and ventral roots of a spinal nerve, and that by their discovery 

 the segmental rank of the olfactory nerve was established. But, as 

 Prof. Wiedersheim has kindly informed me by letter, he has, since the 

 appearance of Blaue's paper (" Ueber Bau der Nasenschleimhaut bei 

 Fischen und Amphibien," 'Archiv fur Anat.,' 1884), seen reason to 

 change his views on this subject. 



The contents of this really important paper will be referred to 

 shortly, and here I need only express my conviction that the results of 

 Blaue's work, taken in conjunction with the light which I hope to 

 throw on the development of the nose and its relationship to the other 

 branchial sense organs, settle in a very definite and satisfactory manner 

 the true homology of the nose. 



What has now to be demonstrated is that the nose is really a 

 branchial sense organ, that is, the sense organ of a non-existent gill- 

 cleft, and not a gill-cleft itself 



It ought here to be mentioned that Hoffmann has already expressed 

 a very similar view of the nature of the nose. 2 That is, he compares 

 its whole development to that of the ear and of the so-called organs of 

 the lateral line, and rejects Marshall's view entirely. 



Although I have very little that is new to add concerning the 

 development of the olfactory nerve, still the novel way in which its 

 development will be regarded is not without importance. 



It was seen in discussing the nerve of the second segment — the root 

 of the ciliary ganglion — that the whole nature of the nerve of this 

 segment was obvious enough when it was noticed that the musculature 

 of the lateral plates, that is, the gill-musculature, was absent, even in the 

 ontogeny. 



1 Wiedersheim, ■ Anatomie der Gymnophionen,' 1879, pp. 59, 60. 



B Hoffmann, " Zur Ontogenie der Knochenfische," 'Arcniv f. Micros. Anat./Bd. xxiii., 

 p. 88. 



