88 ALLEN 



(Fig. I, 15, and Fig. 3, 4), has its origin in the tail region. In 

 passing cephalad it trifurcates when the dorsal fins are reached, 

 the two outer branches receive the superficial networks and the 

 median one the dorsal and ventral branches (Fig. 3. 8 and 9). 

 In front of the fin these branches unite in a common trunk, 

 which upon reaching the cranium bifurcates, each fork making 

 a curve behind the eye to empty into the internal jugular. A 

 median abdominal trunk extends from the ventral fin to the 

 clavicle, where it bends to discharge itself into the sinus of 

 Cuvier. Sometimes, according to Sappey, it bifurcates, and 

 each fork terminates in the corresponding ductus of Cuvier. 

 These six trunks are connected by a series of vessels into which 

 a network of capillaries are discharged. A series of intercostals 

 (Fig. 3, 13 and 14), connect the ventral with the inferior and 

 superior trunks, and an irregular series, further apart, connect 

 the dorsal with the two superior trunks. The chylous vessels 

 as in the ray open into the ductus of Cuvier. 



Sappey found lymphatic glands in the walls of the digestive 

 tract and on the hearts of the ray, dogfish and sturgeon. 



Mayer (18) in a most extensive monograph on the peculiari- 

 ties of the organs of circulation in Selachians describes these 

 subcutaneous vessels in Squatina, To7'pedo, and Raja as veins. 

 On pp. 339 and 340 he states that when a young Scyllium 

 canicula is placed in an aquarium, that the vena -postica of all 

 the vertical fins are plainly visible. If the fish is excited the 

 blood rapidly disappears from these veins, but returns again 

 after a brief rest. With the ordinary swimming back and forth 

 the blood is said to remain in the fins. Sometimes no fluid 

 flowed out of the lateral vein after cutting it ; consequently 

 Mayer reasons because a trunk is bloodless it does not necessa- 

 rily follow that it is a lymphatic vessel. According to Mayer 

 (pp. 366-7 and 9) the subcutaneous veins do not carry pure 

 blood, but rather a mixture of blood, a few small discs, many 

 leucocytes, intermixed with a fluid resembling chyle ; while the 

 intestinal veins commonly contain blood, but at stated times chyle. 

 Mayer has injected the sheaths surrounding the intestinal blood 

 vessels and finds the ch^dous system of vessels as observed by 

 Robin. On p. 368 he severely criticises Sappey for not being 



