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fellow of the opposite side by a cross-corn missural vessel, and then, 

 issuing from the myodome through its orbital opening, it reaches and 

 enters the eye-ball. That part of this artery that lies between the 

 pseudobranch and the cross-commissural vessel, together with one 

 half of the latter vessel, is the efferent mandibular, or properly so- 

 called efferent pseudobranchial artery, that part of the artery that 

 lies anterior to the cross-commissure alone being the true ophthalmica 

 magna and the horaologue of the so-named artery in selachians. 



A dorsal branchial-muscle artery is found arising from the lateral 

 dorsal aorta posterior to the point where that artery is joined by the 

 second efferent branchial artery. 



In the adult Salmo salar I find the arteries, with slight excep- 

 tions, as DoHEN (1886) and Maurer (1888) give them in embryos of 

 the trout. The ventral end of each of the four efferent branchial 

 arteries is double; and from each of these efferent arteries, near the 

 dorsal ends of the gill clefts, a short branch is sent upward on either 

 side to the dorsal gill filaments of the related cleft. Similarly, near 

 the ventral end of each afferent branchial artery a short branch is 

 sent downward to supply the ventral portion of the related gill or gills. 



The afferent mandibular artery has its origin from the efferent 

 artery of the first branchial arch slightly dorsal to the point where 

 that artery separates into its two terminal ventral branches. Running 

 at first downward, and then forward, it sends a small branch upward 

 along the postero-mesial surface of the ceratohyal, this branch quite 

 undoubtedly being, like the strictly similar branch in Esox, a secon- 

 dary afferent hyoidean artery developed from the ventral portion of 

 the posterior efferent artery of the arch. The primary afferent 

 hyoidean artery has, according to Maurer, completely disappeared in 

 25 mm. larvae of the trout, and Mauber does not show either an efferent, 

 or a secondary afferent artery in this arch. According to Dohrn, the 

 primary afferent artery still persists as an important vessel, and is 

 still connected with the ventral aorta, in a 22 mm. trout. 



The afferent mandibular artery, after giving off this secondary 

 afferent hyoidean artery, immediately perforates the hypohyal and 

 turns upward along the antero-lateral surface of that element and 

 then along the corresponding surface of the ceratohyal. Before it 

 reaches the dorsal end of the latter element it sends a branch back- 

 ward, this branch immediately separating into two portions one of 

 which runs upward and the other downward in the hyoidean arch, 



