LYMPHATICS IN TAIL REGION, SCORP^NICHTHYS 



dal fin ray arteries supply the fin rays and the membrane connect- 

 ing them. 



Favaro describes the minor caudal artery in numerous species 

 as the arteria o arteriae longitudinales vasorum intermediorum. 

 His fig. 156 graphically shows the evolution of this vessel. In 

 Squalus it is represented simply as branches from the segmental 

 arteries, which anastomose with the vasa intermedia. In Raja 

 they also have their origin from branches of the segmental arter- 

 ies, but run caudad in the haemal canal for a short distance before 

 anastomosing w^ith the vasa intermedia. In Acipenser they like- 

 wise arise from the segmental arteries and anastomose with the 

 vasa intermedia, and moreover by continuing in the haemal canal 

 to anastomose with the successive segmental arteries they form 

 a continuous trunk which runs parallel with the caudal artery 

 and the vasa intermedia, and at regular intervals, between the 

 intersegmental arteries it sends off anastomosing branches to the 

 vasa intermedia ; while in the Teleosts the arrangement is identi- 

 cal to Acipenser, except that the direct connections of the vasa 

 intermedia or longitudinal haemal lymphatic trunk with the cau- 

 dal vein are lost. 



As stated above in Scorpaenichthys no connections with the 

 intersegmental arteries were observed; hence the minor caudal 

 artery in this species is still further differentiated ; for it is simply a 

 vessel arising from the aorta and passing caudad with it to the tail. 



Caudal vein (figs. 3-6, 9 and 12, C.V.). In Scorpaenichthys 

 and Clinocottus, as in other fishes, this vein traverses the haemal 

 canal immediately below the caudal and the minor caudal arteries. 

 When distended its caliber is much greater than the artery, while 

 its walls are much thinner. Unlike Lepisosteus (p. 51) it does 

 not expand under the last vertebra in a sinus (Sinus venous cau- 

 dalis of Favaro). As represented in Ophiodon elongatus (p. 107) 

 the caudal vein of Scorpaenichthys and Clinocottus bifurcates 

 below the last vertebra into a right and a left branch, which are 

 of different lengths and different relative importance. Some- 

 times the main stem is the right branch, but more often it is the 

 left; while in one instance they were of equal lengths and import- 

 ance. 



