336 



FISHES 



branchial artery of the first branchial arch, the corresponding 

 efferent trunk forming an ophthalmic artery, and passing to the 

 choroid gland of the eye (Fig. 199). Both the proper afferent 

 and efferent arteries of the hyoidean hemibranch either dis- 

 appear or, as in the Cod (Gadiis morrhica), the efferent artery 

 may be represented on each side by an anastomosis between the 

 hyoidean artery and the cephalic circle. Hence, the " hyoidean " 

 artery of Teleosts corresponds to the one which has a similar 

 origin in Lepidosteus. 



A brief description of the remaining efferent branchial arteries 



Fig. 198. — The "branchial circulation in Lepidosteus (diagrammatic), a, a. Afferent 

 branchial arteries ; c, carotid ; d.a, dorsal aorta ; «, e, efferent branchial arteries ; 

 ef.a, efferent vessel from the hyoidean gill which, after its nnion with the hyoidean 

 artery, becomes the afferent vessel of the spiracular pseudobranch ; ef.a\ efferent 

 vessel of the spiracular pseudobranch ; hy.a^ hyoidean artery ; hy.g^ hyoidean 

 gill ; sp.2:>s, spiracular pseudobranch ; v. a, ventral aorta ; 1-5, the hyo-branchial 

 and succeeding gill-clefts. (After F. W. iWiiller and Eamsay Wright.) 



and their derivatives in the Cod (Gadus morrhua) will illustrate 

 the condition of these structures in a well-known Teleost. 



In this Pish the efferent branchial vessels open dorsally into 

 right and left suprabranchial arteries,""" which unite behind to 

 form a median dorsal aorta (Fig. 199). Anteriorly, the paired 

 suprabranchial arteries extend towards the base of the skull as 

 the so-called " carotid " arteries. The two carotids enter the 

 cranial cavity, and there unite in the median line, as in the 

 Cyclostomes. By the union of these arteries in front, and of the 



' These vessels are not to be regarded as homologous with the primitive paired 

 aortae of Amphioxus and the embryos of higher Vertebrates. The true dorsal 

 aorta sometimes persists as a median vestigial vessel which traverses the circulus 

 cephalicus. 



