124 



s.apsb 



the anterior end of the circulus, both of which pairs are marked d; 

 and the vessels d are said by Müller, in the descriptions of the 

 plates, to be distributed to the nose and to the muscles of the eye. 

 This is however probably true of the outer one only of the two pairs, 

 the median pair quite certainly going to the cranial cavity and 

 being formed by the cerebral prolongations of the internal carotids of 

 opposite sides ; for otherwise those prolongations would be wholly 

 wanting in the fish. In my specimen, these cerebral prolongations are 

 represented, as just above stated, by a single median, or encephahc 



artery,which,having 

 ^<^^ perforated the roof 



of the myodome and 

 entered the cranial 

 cavity, there sepa- 

 rates into two parts, 

 one on either side. 

 Each of these two 

 parts forms the 

 arteria cerebralis of 

 its side, and each 

 immediately sepa- 

 rates into anterior 

 and posterior por- 

 tions, the posterior 

 portions of opposite 

 sides fusing posteri- 

 orly, in the median 

 line, and there gi- 

 ving origin to a 

 single median myelonal artery. In T. J. Parker's (1884) diagram of 

 the vascular system of Gadus morrhua, these cerebralis arteries are 

 even less well accounted for than in Müller's figure, for Parker 

 shows but a single pair of arteries arising from the anterior end of 

 the circulus cephalicus, and that pair, although called by Parker the 

 carotid arteries, has the position of the outer one of the two- pairs 

 in Müller's figure ; that is, the position of the orbito-nasal arteries 

 in my specimen. Boulenger, in a figure of the branchial arteries of 

 this same fish, on page 337 of the volume "Fishes, Ascidians, etc." 

 of The Cambridge Natural History (1904), here shows a single median 



/hbr 



mhbr 



Fig. 4. Diagrammatic representation of the arteries 

 shown in Fig. 3. 



