53 William F. Allen 



the caudal sinuses. Likewise Hyrtl/ in Figs. 1, 2 and 4, V., represents 

 the caudal vein in Esox (= Lucius) and Leuciscus as terminating 

 under the last vertebra, and receiving a papilla from each of the caudal 

 sinuses. With the bony fishes Sappey* (p. 46) states that the caudal 

 vein takes its origin in two branches from the base of the caudal find 

 and is so figured in the pike (PL XII, Fig. 2, 7). With the Selachians 

 and Polyodon the structure of the caudal fin is so different that a 

 comparison is hardly permissible. Mayer^ (p. 325) finds that the caudal 

 vein extends much further caudad with the dogfish than with the 

 roaches. With the latter it may become paired, then reuniting, finally 

 terminates, and its place farther caudad is taken by branches that form 

 a vasa vasorum with similar branches from the caudal artery. 



The distribution of the caudal artery and vein doubtless conforms to 

 the same general plan in all fishes, but in a great many excellent papers 

 on the circulation of blood in fishes there has been a marked tendency 

 to overlook the final ending of the caudal artery in the caudal fin and 

 the origin of the caudal vein from the same. It may be that the caudal 

 vein in some fishes is not continued into the caudal fin, but I mistrust 

 in those instances that the injection mass has failed to reach the 

 posterior end of this trunk. If such' were not the case, it would 

 materially strengthen the hypothesis that the subcutaneous vessels which 

 came from the tail and emptied into the caudal sinuses and then into 

 the caudal vein were veins rather than lymphatics. 



Intercostal Arteries and Veins. — These are among the most important 

 branches of the caudal artery and vein. Ordinarily, as with the Teleosts, 

 a neural and h^mal artery arise from under each alternate vertebra, 

 and a neural and haemal vein empty into the caudal vein beneath the 

 intermediate alternate vertebrge. The haemal vessels follow the hamal 

 spines, and the neural vessels after crossing their respective vertebra 

 run along the neural spines. From some of the neural arteries and 

 veins, but not from all, a lateral artery or vein (Fig. 8, L. A. and L. V.) 

 is given off or received. Tracing these vessels, laterad, they are found 



^Hyrtl, Jos. "Ueber die Caudal uud Kopf-Siuuse der Fische, uud das 

 damit znsammenhangende Seitengcfilss-System," Archiv fiir Anatomie und 

 Physiologic, pp. 224-240, 1843. 



*Sappey, P. C. "Etudes sur I'appareil mucipare et sur le systeme lym- 

 phatique des poissons." pp. 1-G4, Paris, 1880. 



"Mayer, P. "Ueber Eigenthiimlicblveiten In den Kreislaufsorganen der 

 Selacbier," MitthoiUmocn avs der zooJog'ischen Station zu Ncapel, VIII Bd., 

 1888. 



