PLATE 9 



EXPLANATION OF FIGURES 



This plate illustrates the development of the submaxillary lymphatics in the third 

 period. E. palustris. Figure 18 demonstrates the plexiform condition of the tem- 

 poral sinus and jugular lymphatic in early injections. Numerous processes invade 

 the suborbital tissues. The earliest lymphatics of the submaxillary region, drawn 

 in figure 20, are simple ducts connected laterally with the temporal sinus. Cireuni- 

 oral and mandibular processes project forward from a central duct (Cn.S.). The 

 pericardial lymphatic reaches the system from behind without connecting with 

 the cavities. The inset on the right gives these vessels from a ventral view (V.). 

 Figure 21 is drawn from the same specimen as figure 14, as are also the sinuses 

 on the right (R.). The sinuses on the left (L.) are introduced from a different 

 specimen. The lymph sinuses on the right (E.) are fully distended with the 

 injection fluid, which has broken through to fill the pericardial sinus at the back. 

 On the left (L.) only sufficient fluid has entered the central sinus to outline its 

 walls, and, since the pericardial sinus receives its injection from the back, it ends 

 distally against the outer surface. The central sinus has been dissected off from 

 the left side of the specimen in figure 21a, revealing the connections of the 

 underlying central duct with the mandibular and circum-oral processes. 



106 



