Pseudobranchial and Carotid Arteries in the Gnatliostome Fishes. 113 



all the selachians I have considered, excepting only CJiJamydoselacJms; 

 and the external carotid has its origin from the dorsal aorta posterior 

 to this point of anastomosis and anterior to the hyoidean aortic 

 arch, as in most selachians. 



In Torpedo, the vessels are practicallj' as in Raja, excepting 

 that there are no afferent or efferent pseudobranchial, or ophthalmica 

 magna arteries; these arteries being found in young embryos of 

 Torpedo, but, according to Dohkn (1890, p. 415), soon aborting, and 

 in 28 mm embryos being wholly resorbed. The external carotid is 

 shown by Htetl definitely running dorsal to the optic nerve, instead 

 of ventral to it; but this may be in error, for Dohrn's (1890, 

 p. 412) description of the course of the artery in embryos would 

 certainly seem to indicate that it lies posterior and ventral to the 

 nerve. An important branch is sent from this artery to the 

 spiracular canal, the branch breaking up in the constrictor muscle 

 and the mucous membrane of that canal, and also in the "kaum 

 mehr kennbaren sogenannten Nebenkieme" (Hyrtl, 1858, p. 7) : and 

 if Hyktl's figure of Torpedo be compared with his figure of Raja it 

 will be seen that this branch of the external carotid of Torpedo 

 corresponds strikingly in position, and in general relations to the 

 other vessels, to the portion Jc of the efferent spiracular artery of 

 Raja. So striking is this similarity that one is led to wonder if 

 there may not be some error here, either in observation or in the 

 figure; or if, perhaps, this branch of the external carotid of the adult 

 Torpedo may not, in embrj^os, have been connected with the so-called 

 ophthalmic branch of the internal carotid, which passes so close 

 to it. instead of with the external carotid. This branch of the ex- 

 ternal carotid, together with the proximal portion of the arteria 

 ophthalmica of Hyrtl's descriptions would then constitute an efferent 

 mandibular artery strictly similar to that of Raja, and the distal 

 half of the arteria ophthalmica of Hyrtl's descriptions of the adult 

 would be the ophthalmica magna of embryos. And that this latter 

 supposition may be the proper one would seem to be indicated by 

 certain of Rafpaele's conclusions. 



Rafpaele (1892) finds, in young embryos of Torpedo, that the 

 mandibular aortic arch of either side curves inward near its dorsal 

 end, and immediately in front of the blind anterior end of the gut, 

 touches and coalesces, in the middle line, with its fellow of the 

 opposite side, to form a large median cephalic vascular sinus. The 

 two arteries are then said, on p. 447, to separate again, and running 



Zool. Jahrb. XXVII. Abt. f. Anat. 8 



