PLATE 19 



EXPLANATION OF FIGURES 



The superficial veins, shown in figure 39 for a 10-mm. larva of R. palustris 

 with rounded-up body, are grouped in two sets, the anterior plexus increased by 

 contributions from the cutaneous artery, ending in the first two intersegmental 

 veins; while the anterior vertebral is now a distinct channel, continued ventrally 

 through the third vein. The connecting vessels from the deep plexuses of this 

 system are well defined. Figure 40 represents a very complete injection of the 

 blood vessels of a 12 mm. larva of E. palustris, in which the segmental veins are 

 still visible, though overgrown by the extensive superficial plexus. The anterior 

 vertebral vein is now a distinct dorsolateral trunk, with outflow through the third 

 vein. The superficial plexuses with additions from the cutaneous artery reach the 

 first and second intersegmental veins through definite channels; the posterior 

 vessels draining through the second, while the anterior and facial connections are 

 to be traced into the third vein. The use of a hand lens makes it possible to 

 identifv the details. 



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