THE ELASMOBRANCH FISHES 217 



doul)le vein tlio parts of wliicli later unite to form the rena profunda of Mayer. 

 Further, in Squaliis tlie voia profunda joins the i)ostcardinal vein. In Mus- 

 felus henlei if the deep vessel ])asses to the right of the column it breaks up 

 in a leash of vessels and may join the renal portal vein. In Heptanchus macu- 

 latus a similar vessel in the region of the single dorsal fin, which is com])aral)le 

 to the second dorsal fin of Squalus, passes to the right of the column and joins 

 the caudal vein. The vena profunda of the second dorsal loop in Sqiialus and 

 in Musfelus Jienlei joins the caudal vein. 



The lateral cutaneous veins (l.cv., fig. 198) accompany the lateral line sys- 

 tem, the main trunk of the lateral cutaneous passing just mediad of and ven- 

 tral to the lateral line. They collect blood from dorsal and ventral branches 

 to the corium and underlying connective tissue and empty anteriorly into the 

 subscapular sinus (s.scv.), which in turn enters the postcardinal sinus except 

 in types like Heptanchus. A system of cross-trunks in the regions of the dorsal 

 fins puts the lateral cutaneous in connection with the dorsal cutaneous vein 

 (c, fig. 199a). In a number of Elasmobranchs (Squalus sucklii, fig. 198) an 

 accessory lateral cutaneous vein (l.c.v.'^) extends from the pelvic to the pec- 

 toral segments, parallel with the lateral cutaneous proper. This vessel has 

 segmental connections with the lateral cutaneous above it and the ventral 

 cutaneous below it. 



The ventral cutaneous vein is divided into pre- and postcloacal parts 

 ip.v.c. ) . The precloacal part, not shown in figure 199b, extends as an unpaired 

 median vein between the pelvic and pectoral regions. In the region of the 

 pectoral it bifurcates, sending a right and a left branch to the lateral abdomi- 

 nal vein. These branches seem to be the same as those which I described for 

 Heptanchus maculatus as the coracoid veins (Daniel, 1918) . Posteriorly in the 

 pelvic area, the vessel also divides (pi., fig. 199b). Here its right and left 

 branches in Squalus sucklii empty into a sinus (s.), from which the blood 

 enters the lateral abdominal vein {l.a.v.). 



The postcloacal division of the ventral cutaneous extends from the tail to 

 the cloacal area. It arises as a pair of vessels on the right and left sides of the 

 caudal fin, which do not meet around the tip of the ventral lobe of the fin. These 

 vessels communicate with the caudal vein. If an anal fin be present (Scyllium) 

 the ventral cutaneous forms a loop around the anal fin and then extends to 

 the cloaca (p.c, fig. 199b) , bifurcating into right and left branches. The blood 

 collected by this vein also passes into the sinus (.s-. ) and thence into the lateral 

 abdominal system. 



NATUEE OF CUTANEOUS SYSTEM OF VESSELS 



It was early observed that the cutaneous vessels in Elasmobranchs are not 

 accompanied by arterial trunks. From this fact it was argued that they are 

 not blood vessels but are lymphatic in nature. Work done by Miss Coles (1928) 

 in this laboratory, however, showed that while no longitudinal arterial trunks 

 accompany these vessels in Squalus sucklii, yet they are provided with a rich 

 arterial supply which is given off by branches from the segmental arteries. 



