22 WILLIAM F. ALLEN 



Caudal Lymphatic trunks.— Of these vessels, those coming from 

 the basal canal of the caudal fin, namely, the dorsal and ventral 

 caudal fin lymphatic trunks (figs. 3-7, C.T. o and (2)) are very large 

 and important vessels occupying most of the space in this canal, 

 and for a considerable distance they run parallel to correspond- 

 ing blood vessels and nerves. In the median line the dorsal and 

 ventral trunks anastomose, and the trunk thus formed extends 

 cephalad a short distance between the posterior ends of the 

 hypural bones, where it expands into a small sinus, designated as 

 the posterior caudal sinus. As previously stated the dorsal caudal 

 lymphatic trunk unites with the dorsal lymphatic trunk a little 

 anterior of the base of the caudal fin, and at the point of union 

 they are joined by a greatly enlarged neural trunk{hgA,Neu.T.(i)), 

 which occupies a large part of the space between the neural spines 

 of the third and fourth vertebrae from the last, and terminates 

 in the longitudinal neural lymphatic trunk opposite the third 

 vertebra from the last. A similar arrangement is found in con- 

 nection with the ventral caudal fin lymphatic trunk, which together 

 with the ventral lymphatic trunk fuse as shown in fig. 4 with the 

 last two haemal lymphatic trunks {Hoe.T. (d and (2)). Possibly 

 a more correct rendering of these relationships would be to con- 

 sider the next to the last neural trunk (fig. 4, Neu.T.a)), and the 

 last two haemal trunks (figs. 4, Hw.T. u) and (2)) as continuations 

 of the dorsal and ventral caudal fin lymphatic trunks, which 

 empty directly into the longitudinal neural and hasmal lymphatic 

 trunks. With this interpretation the dorsal lymphatic trunk 

 would be said to empty into the dorsal caudal fin lymphatic trunk, 

 and the ventral lymphatic trunk into the ventral caudal fin lym- 

 phatic trunk. 



Throughout their course through the basal canal of the caudal 

 fin both caudal fin lymphatic trunks receive numerous caudal ray 

 lymi)hatic trunks (figs. 3-5, and 7, C.R.T.) ; two of which traverse 

 the dorsal and ventral surfaces of each caudal ray. They collect 

 a rather course network, decidedly lymphatic, in the character 

 of its meshes, and which so far as could be determined had no 

 connections with the arterial system, from the fin membrane con- 

 necting two rays. Ordinarily, especially in the extreme dorsal 



