EXPLANATION OF THE PLATES 



PLATE I. 



Figs. I to 17 were'drawn to a scale from injected specimens ; 18 to 21 are from 

 microscopic preparations of injected material; and 22 to 27 are from sections. 

 In general the arteries are stippled, the veins are cross-barred, and the so-called 

 lymphatic trunks are drawn in outline. A vessel drawn in dotted outline signi- 

 fies that it passes within or behind a bone, muscle or organ. All outlines for 

 the microscopic drawings were made with a camera lucida and the details were 

 filled in afterward. 



Fig. I. Represents a general lateral dissection of a 70-pound Polyodoti 

 spathula head as seen from the left side and above. Most of the paddle or spoon, 

 all of the opercle and branchial arches, a part of the shoulder girdle, and the left 

 wall of the brain case were removed so as to best portray the vessels. X \- 



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