516 ALLIS. [Vou. XII. 
opening of the orbito-nasal canal and the anterior end of the 
lobus. The orbito-nasal canal in such specimens, at its anterior 
end, turns upward almost at right angles to the olfactory nerve, 
and immediately under and lateral to that nerve. In still later 
stages the olfactory nerve is enclosed above and in front of the 
opening of the orbito-nasal canal, and the anterior part of the 
olfactory canal of the adult is formed. The lobus olfactorius 
during the same period recedes, with the brain, from the ante- 
rior end of the cranial cavity, and the long intracranial portion 
of the nervus olfactorius is formed. There is never the 
slightest indication of a tractus olfactorius. 
The development of the olfactory parts in Amia thus agrees 
exactly with that in the trout, as described by Sagemehl (No. 
106, p. 76), and in the adult Amia, as well as in embryos, its 
nervus olfactorius lies in a certain limited part of its course 
exposed in the orbit. Amia, therefore, in this respect belongs 
definitely to Sagemehl’s third or teleostean type, and it and all 
ganoids and teleosts are in all probability derived directly from 
his cyclostome type and not from the selachian type, as he con- 
cludes (No. 104, p. 219). In those teleosts that have a tractus 
olfactorius I agree with Lee that they owe it, as do the elasmo- 
branchs, 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 
arrangement resulting from them. 
5. Muscles of the Eye, Nervus Oculomotorius, Nervus Trochlearis, 
and Nervus Abducens. 
The obliqui muscles (os and oz, Figs. 21-27, Pls. XXIV and 
X XV) arise, in the adult, close together from the side wall of 
the orbit at its extreme front end immediately below the orbito- 
nasal fenestra. A slight depression, occupying the space between 
that fenestra and the floor of the orbit, marks the place of origin, 
and is unquestionably the small beginning of the anterior eye- 
muscle canal of certain teleosts (No. 107, pp. 563 and 566). In 
