PLATE 1 



EXPLANATION OF FIGURES 



All the figures (except 10, 13 a, and 16) were drawn with the Abbe camera 

 lucida. Most of them have been reduced one-third in reproduction; the magni- 

 fications are after this reduction. 



1 View from the ventral surface C. marginatum, from a specimen from the 

 throat of Ardea herodias, fixed under compression in aqueous corrosive sublimate, 

 borax-carmine. X 12. 



2 A partly schematic view from the dorsal side, combining facts from several 

 sections from a frontal series. From a bass worm. The vitellaria are not yet 

 developed, the uterine sack is not dilated, the excretory collecting vessel is omit- 

 ted from the right side and the recurrent vessel from the left, parts on different 

 levels are shown on the same level. X 27. 



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