Subcutaneous Vessels in Tail of Lepisosteus (55 



cit., p. 49) as following along in the same canal with the caudal artery 

 and vein. A similar vessel is also noted by Sappey (p. 50) for Pleuro- 

 nectes. In PI. XII, Sappey represents this trunk in the pike (Fig. II, 

 10) and in Pleuronectes (Fig. TV, 17) as receiving numerous hsemal 

 or intercostal vessels, but its posterior ending is not given; from his 

 figures, however, it appears to end blindly before the base of the tail is 

 reached. 



In addition to the caudal artery and vein, Mayer (op cit., p. 320) 

 finds a longitudinal trunk in the haemal canal of Scyllium, Mustelus 

 and Squatina, Avhich he takes to be a vein that collects a vasa vasorum, 

 originating from little paired arteries that leave the caudal artery 

 between the intercostal arteries (PI. 17, Fig. 11, avas.). Again, 

 further on (pp. 325-6), Mayer states that the caudal vein is very 

 irregular, changing from side to side, becoming paired, then unpaired, 

 to finally disappear altogether, and its place is taken by a vasa vasorum 

 (haemal trunks). After which there is nothing in the haemal canal but 

 the caudal artery in the center, surrounded by connective tissue and 

 small blood spaces. Mayer conjectures that possibly in the past these 

 blood cavities had a different function, that they may have been derived 

 from a degeneration of the body cavity. Hopkins does not record any 

 such trunk for Amiatus. 



Caudal Sinuses. — These sinuses have received considerable attention 

 from all workers on the subcutaneous system of fishes. Naturally thev 

 fall into two classes: pulsating hearts resembling the lymphatic hearts 

 of the Batrachians, and non-pulsating sinuses. In some fishes or fish- 

 like vertebrates that swim by a snake-like movement, we find a pul- 

 sating heart in the tail; while in other fishes which swim by a lateral 

 movement of the tail, the caudal sinuses are simply reservoirs, and 

 strange to say with the Selachians no such receptacle has been found; 

 in this group the subcutaneous trunks empty directly into the caudal 

 vein. 



Greene^^ and Klinckowstrom^^ found two pulsating caudal hearts in 

 the tails of Polistotrema {^= Bdellostoma) and Myxine. Each of these 

 hearts, which are separated from one another by the median caudal 



"Greene, C. W. "Contributions to tlie Physiology of the California Hag- 

 flsh, Polistotrema stouti : 1. The Anatomy and Physiology of the Caudal 

 Heart," American Journal of Physiology, Vol. III. 1900. 



'-Klinckowstrom. A. Title not known. TerJiandlungen dcs hiologischeii 

 rcreins in StocJchohu, 1890 and 1891. 



