141 



aorta, the conditions of these vessels in Esox and Gadus would arise. 

 And if the orbital branch of the carotid of Amia, or of selachians, 

 were also to be split off from the main artery and to acquire inde- 

 pendent origin from the lateral dorsal aorta the orbito-nasal artery of 

 teleosts would arise. 



These homologies all seem too probable not to be proposed, and 

 they are shown diagrararaatically represented in the accompanying 

 figures 2, 4 and 6. 



To what extent the vessel x of my descriptions is also developed 

 from portions of the hyoidean arterial arch, now seems problematical. 

 In a 43 mm. larva of Amia I find this vessel arising in a glomus 

 that lies mesial to the dorsal end of the first branchial arch, and 

 this glomus is supplied by a small branch of the hyo-opercularis 

 artery. Running forward from this glomus the vessel x separates into 

 two parts, both of which traverse the trigemino-facialis chamber, no 

 branch being sent downward through the facialis canal in the hyo- 

 mandibular. Of the two branches that traverse the trigemino-facialis 

 chamber one closely accompanies the hyo-opercularis and the other 

 the external carotid. But before issuing from the trigemino-facialis 

 chamber, into the orbit, the branch that accompanies the external 

 carotid sends a large branch to join and fuse with the branch that 

 accompanies the hyo-opercularis. The single vessel so formed then 

 accompanies but does not fuse with the orbital prolongation of the 

 hyo-opercularis, the two arteries having the position, in this larva, 

 of that branch of the orbital branch of the external carotid of the 

 adult that receives a communicating branch from the hyo-opercularis 

 and then, as a single vessel, accompanies the ophthalmicus nerves. 

 It thus seems probable that a part of the vessel x of this larva is 

 represented in a part of the orbital branch of the external carotid 

 of the adult. Similarly the facialis branch of the external carotid of 

 certain specimens of the Loricati may be represented, in other specimens 

 of those same fishes, by a branch of the vessel x, both of these vessels 

 being represented in Amia by a part of the hyo-opercularis. This 

 all seems to indicate that the efferent hyoidean artery, which, because 

 of the abortion of the hyoidean gills, is in process of disappearing, 

 is being absorbed or utilized by both the external carotid and the 

 vessel x; but to what extent it is appropriated by each of these two 

 vessels is quite uncertain. 



Palais de Carnoles, Menton, France, January 22°^ 1912. 



