474 On the Blood-vessels of Mustelus antarctic us. [June 10, 



and the lateral veins, and are directly continued one into each end of 

 the sinus venosus. 



The jugular veins receive the blood from the orbital and hjoidean 

 sinuses ; the anterior cerebral and anterior facial veins discharge into 

 the orbital sinus, the posterior facial and nutrient hyoidean veins 

 into the hyoidean sinus. The posterior cerebral and myelonal veins 

 open by numerous commissures into the jugular, cardinal, renal portal, 

 and caudal veins. 



The inferior jugular receives a nutrient branchial vein from each of 

 the four holobranchs, and anastomoses in front with the hyoidean 

 sinus. 



The cardinal veins are asymmetrically developed, only the right 

 being complete. The latter arises by the confluence of the efferent 

 renal veins, and, passing forwards, joins with the left cardinal. Each 

 vein dilates anteriorly into a cardinal sinus, which communicates with 

 its fellow by a wide aperture, that of the right side receiving a large 

 spermatic vein. 



There is a large anastomotic trunk between the spermatic and 

 portal veins. 



The lateral vein receives the veins from the pectoral and pelvic fins, 

 and unites with its fellow across the dorsal aspect of the pubic 

 cartilage. 



The lateral vein is considered to be homogeneous with the epigastric 

 or anterior abdominal vein of amphibia and reptiles ; it is also sug- 

 gested that it may be derived from the vein of the hypothetical 

 lateral fin of the proto-vertebrata, and possibly also from the primary 

 lateral vessel of the proto-chordata. In this connexion some recent 

 speculations on the phylogeny of the chordata are discussed in their 

 bearing on the vascular system. 



There are two coronary veins opening into the sinus venosus. 



The cutaneous veins are five in number, a dorsal, an anterior and a 

 posterior ventral, and a pair of lateral vessels. The dorsal cutaneous 

 vein opens into the left renal portal, the anterior ventral into the 

 lateral veins anteriorly and into the iliacs posteriorly, the posterior 

 ventral into the cloacal veins, and the lateral into the subscapular 

 sinus. The dorsal and the posterior ventral vessels form closed loops 

 round the bases of the median (first and second dorsal and ventral- 

 anal) fins. The lateral cutaneous vein anastomoses posteriorly with 

 the caudal and with the dorsal cutaneous vein. 



Attention is drawn to the large number of anastomoses between 

 important arteries and veins, and to the sinus-like or lacunar 

 character of many of the venous channels. 



