264 LIONEL JAMES PIOTON. 



Clapai'ede (9, A, p. 399) ' meutions in the dorsal vessel of 

 Terebella multisetosa " une substance d'un noir profond, 

 distribuee en cordons irreguliers ; " and describes a similar 

 structure also in the Cirratulidse. He further notes (9, B) 

 that chloragogeuj the so-called " liver ^^ tissue of Annelids, 

 which usually clothes the gut and the exterior of the chief 

 blood-vessels, is entirely absent in those forms in which "les 

 masses intravasculaires '' are known to exist. 



Salensky (28) describes its state in the larva of Terebella 

 Meckelii. Though not observed at the earliest period, at a 

 certain stage an opening in the wall of the vessel was noted, 

 which led into the cardiac body. Salensky does not state the 

 exact position of this orifice, but says, " II s'ouvre d^abord 

 dans un petit tube bien etroit et se continue ensuite dans le 

 corps cardiaque, qui a ce stade du developpement represente 

 un organe de forme cylindrique." For the rest, the state of 

 the heart-body is described as being much the same as in 

 the adult. 



In the Chlorhaemidse many naturalists have observed the 

 peculiar dorsal vessel which appears to spring from the wall 

 of the gut, and is of a very deep colour on account of the 

 heart-body contained in it. Horst (16) describes the mis- 

 taken views of Otto, who thought it was a second cesophagus ; 

 of Dujardin, who regarded it as a mere blood-vessel; of 

 Claparede, who thought it was a gland opening into the 

 pharynx, and of others ; and himself considers that it is not 

 merely the heart, nor a gland only, but that it is a gland 

 contained in the heart. He thus combines the views of 

 Dujardin and Claparede. He further holds that the heart- 

 body is derived from a pouch of the gut comparable with that 

 of Enchytrseidse. 



Kennel (20) considers a structure in the dorsal vessel of 

 Ctenodrilus as the homologue of the heart-body of Terebella. 



Steen (32, p. 42), in the case of Terebellides Stroemii, 

 thinks the heart-body has a valvular function, preventing a 



' The uumbers refer to the Bibliography at the end of the paper. 



