70 



HENRY MCELDERRY KNOWER 



It has been pointed out on a previous page that, in some 

 injections of early stages, additional connections are revealed 

 between the plexus surrounding it, and both the anterior and 

 posterior walls of the heart ; but such connecting vessels are 

 seldom large (fig. 4 is very exceptional), and do not develop 

 further nor persist, to become increasingly important, like the 

 dorsal afferent portals of the heart. These relations are dis- 

 cussed in detail in the descriptions of figures 3, 4, 5, 6, etc. 

 (pp. 26, 27). 



Figs. D and E These figures are reproductions of two figures from Hover's 

 paper of 1905, figure D representing his figure 1, a dorsal view of his injectons of 

 a 26-mm. larva of R. temporaria; while figure E is his figure 2, a lateral view 

 of the same larva. 



The transformation of proximal vessels of the dorsal heart 

 plexus into tubular ducts which unite in a common reception 

 duct (Dsl.R.D.) or chamber, opening into the dorsal wall and 

 sharply differentiated from the afferent lymphatics from the 

 periphery, has been described in connection with figures 13, 

 14, 15 and 16. In those specimens, the beginning of the inva- 

 sion of the anterior body wall by vessels over the pronephros 

 and the first lymphatics of the posterior body wall are seen. 



In the period of development following the establishment 

 of the conditions here described, there is growth and expan- 

 sion in the plexuses, but the changes in the lymphatics of the 



