DISTRIBUTION OF LYMPHATICS IN SCORPyENICIITHYS 7 1 



expansion of the cranial lymphatic trunk ; a trunk that is formed 

 by the union of the lateral and myelonal canals. 



8. PERICARDIAL SINUSES. 



Strange to say so far as could be determined Hopkins (8, p. 

 372—3) is the only one to describe such a sinus ; evidently it is 

 absent in the other species studied or else it has been over, 

 looked. The ventral lymphatic trunk in „ \111ia is represented as 

 branching at the level of the heart ; each fork running between 

 the pericardium and the tough fibrous partition separating the 

 pericardial from the abdominal cavity, is said to merge into 

 large pericardial sinuses that communicate with the sinuses of 

 the lateral trunk (cephalic sinuses). With Scorpcenichthys this 

 is a very large and extremely important sinus, and appears to 

 be made up of several divisions or sub-reservoirs, which have 

 for convenience been designated as the main pericardial, pos- 

 terior, and ventral pericardial sinuses. 



One of the main pericardial sinuses (Figs. 4, 6, 9 and 10, 

 Per.S.) is perhaps best shown in Fig. 6, which is drawn from 

 a very large specimen that was well injected and hardened in 

 formalin. It is a retort-shaped reservoir situated directly behind 

 the precava or ductus of Cuvier. Its dorsal stem crosses the 

 corresponding lobe of the kidney to unite with the main lateral 

 trunk. In this specimen a branch was given off caudad at the 

 base of the kidney which anastomosed with a branch of the 

 pectoral sinus that emptied into the abdominal sinus. In no 

 other specimen was this connection noticed, but a little below 

 this level and in front there is always some communication with 

 the abdominal sinus. Here a much larger branch is given off 

 cephalad (Figs. 4 and 6) which soon expands into 3 large 

 divisions (Fig. 6 ; a, b and c). The most anterior one (a) passes 

 cephalad to terminate in the abdominal sinus directly behind 

 the precava. The middle one (b), which is the largest of the 3, 

 is a blind sac that extends ventrad directly behind the precava 

 and rests on the dorsal surface of the sinus venosus. Without 

 carefully dissecting out sinus (/;) it always has the appearance 

 of emptying into the sinus venosus. I have, however, carefully 

 dissected out this sinus in many specimens to make certain that 



