HEAET-BODY, ETC., OF CERTAIN POLYCH^TA. 263 



On the Heart-body and Coelomic Fluid of 

 certain Polycliseta. 



By 

 Lionel James Pictoii, B.A. 



With Plates 19—22. 



[This work was doue at Naples during my tenure of the Oxford Scholar- 

 ship there in 1896-7. 



Besides the subjects mentioned in the title, there is a description of a new 

 bow-shaped corpuscle in Notomastus profundus on p. 268, foot- 

 note; and an appendix at the end of the paper concerning intra-vitam 

 staining of nuclei of the gut-wall with carmine in sea-water. — 

 L. J. P.] 



In several groups of Polychaeta there is found in the dorsal 

 vessel or " branchial heart " a rod-like structure usually 

 attached anteriorly and posteriorly, and sometimes at other 

 points, to the vascular walls ; but otherwise lying in the lumen 

 of the tube freely. It is in many instances of a deep brown 

 colour, due to the presence of numerous pigment granules 

 deposited in it. The cells in which these are contained are 

 small and thick-walled. They have little protoplasm, but 

 well-marked nuclei. This organ, under the various names 

 " corps cardiaque,'^ ^^ Herz-Korper,^^ " second oesophagus,^' 

 *' caecum gastro-cesophagien,^' and others, has been discussed 

 by several authors. 



