56 William F. Allen 



imbedded in a mass of fibrous connective tissue. A few red corpuscles 

 were found in this trunk throughout this series. In Figs. 18 and 19 

 several of the caudal rays, together with their blood vessels and sub- 

 cutaneous canals, are seen in section. These subcutaneous canals or 

 lymphatics are readily distinguishable from the blood vessels on account 

 of their larger size, and by the additional fact that they frequently 

 surround the blood vessels to a considerable extent. 



With the Selachians, Mayer (op. cit., pp. 316-7) is the only writer to 

 throw much light on the caudal termination of the vena ventralis, as 

 he styles it. Like the dorsal vein, he finds it paired at the origin of 

 the tail, each fork ending in its corresponding lateral vein, and these 

 latter being in communication with the caudal vein. Parker {op. cit., 

 p. 721) notes with Mustelus that the posterior ventral vein forms a 

 loop around the anal fin, and after bifurcating at the cloaca, each fork 

 anastomoses with its corresponding cloacal vein. iVs with the Selachians, 

 there has been a notable silence concerning the caudal termination of 

 the ventral subcutaneous trunk in the Teleosts. With Pleuronectcs, 

 Sappey {op. cit., p. 49) finds that the ventral lymphatic tnmk (PI. XIT, 

 Fig. YI, 4) is continuous with the caudal and dorsal trunks and forms 

 an ellipse around the body, Avhich ends ventro-cephalad in the ductus 

 of Cuvier and dorso-cephalad in the jugular vein. With Amiatvs, 

 Hopkins {op. cit., pp. 372-3) represents the ventral trunk (PL II, Fig. 

 11, 0. and V.) as arising ,from the base of the caudal fin, and extending 

 cephalad along the ventral side of the body to the heart, where it ends 

 in the pericardial sinuses. In one instance an anastomosing trunk 

 (Fig. 11, t) connects the tail part of the trunk with the lateral trunk, 

 as the latter bends mesad to join the caudal sinus. This communica- 

 tion recalls a somewhat similar arrangement in Lepisostcus, where the 

 caudal trunk or the posterior continuation of the ventral trunk was 

 just described (p. 55) as terminating in the right caudal sinus after 

 traveling through the basal canal of the tail. 



Dorsal Subcutaneous Trunk (Figs. 1-3, 5, 10, 12-13, D. T.). — In 

 many respects this trunk in Lepisosteus is similar to the ventral canal. 

 It follows the dorsal median line in a layer of tough connective tissue 

 that binds the great lateral muscles together. As stated in an earlier 

 paper {op. cit., pp. 113-4), when not far from the posterior end of the 

 skull it empties into the left branchial sinus, which is in direct con- 

 nection with the cephalic sinus, and through the latter it reaches the 

 jugular. When the dorsal fin is reached, instead of forming two 



