288 
Amphibia the fila olfactoria pass from the nasal membrane to the brain 
without the intervention of a tractus. 
In the Reptiles as LEE?) points out both conditions are met with. 
In Anguis fragilis, Amphisbaena and Typhlops there is no tractus, 
but in Hatteria punctata and Lacerta a tractus is present. 
In Amia, Aruıs has figured and described a long olfactory nerve 
but “there is never the slightest indication of a tractus olfactorius” 
(p. 516) ?). 
In Teleosts, also, both conditions are found, as shown in many 
figures in various memoirs. The presence of a bulb and tractus is 
figured by Fritsch?) in Cyprinus sp. and its absence in Lophius pis- 
catorius, Uranoscopus scaber etc. In these cases the superficial resem- 
blance of tractus and nerve proper is very close. ALLiIs*) says: “In 
those Teleosts that have a tractus olfactorius I agree with Lex that they 
owe it, as do the Elasmobranchs, to special mechanical conditions that 
have tended to hold the anterior end of the lobus in its embryonic 
position near the nasal membrane. The separate development of the 
orbito-nasal and olfactory canals, instead of their fusion as in Amia, 
would seem to be either among those conditions or a secondary arrange- 
ment resulting from them.” 
The fact that the olfactory nerve arises before the lobe should 
also be emphasized. In this connection I wish to observe that Ler’s 
diagramatic Fig. 3°) carries a wrong idea, it shows the lobe as 
having developed before the olfactory fibres. 
The generalization of OskKAR HERTwIG quoted above is based on 
the highly modified and special condition found in Selachii and can 
not be supported either by comparative anatomy or development. The 
facts of development and comparative anatomy serve rather to show 
the similarity of the olfactory nerve to the other cranial nerves than 
to place it in a special category. 
The olfactory nerve in Selachians (fila olfactoria in front of the 
bulb) has for a long time been represented as double but very little 
has been said about it in descriptions of Figs. or in texts. LEURET 
and GRATIOLET ®) show it in their Pl. II, Fig. 2, MiktucHo-Mactay ’70, 
mentions this condition and figures it, RoHon’ 78, quotes the latter and 
figures it, etc. In the Amphibia also it has been frequently figured 
1) Berichte Naturf, Gesellsch., Freiburg, Bd. 7, 1893. 
2) Journ. Morph., Vol. 12, 1897. 
3) Untersuchungen über den feineren Bau des Fischgehirns, 1878. 
4) loc. cit. 
5) loc cit. 
6) Anat. comp. du systeme nerveux, 1889—1857. 
