HEART-BODY, ETC., OF CERTAIN POLYOH^TA. 265 



back-flow caused by the contracting gills. He describes it as 

 enclosed in a fine membrane. 



Eisig (12, p. 691) mentions the statements of the earlier 

 writers on the heart-body. First, ordinary chloragogen is 

 absent in the forms which have a heart-body, whilst the 

 heart-body is very similar to chloragogen tissue. He there- 

 fore proposes to call it '^ intra-vascular chloragogen.'^ Secondly, 

 he considers that Salensky^s statements make it very probable 

 that it is derived from the wall of the dorsal vessel and from 

 peritoneal tissue, from which the coelomic corpuscles^ are also 

 produced. This is equivalent to saying that chloragogen, 

 which is a modification of peritoneal tissue, instead of remain- 

 ing on the outside of the dorsal vessel, becomes folded so as 

 to occupy its interior. Both to coelomic corpuscles and to 

 chloragogen excretory functions have been attributed, and this 

 view regards them as having a morphological connection. 



Cunningham (10) describes the heart-body in Cirratulidae, 

 Cblorheemidse, and Terebellidse, and mentions its occurrence 

 in Amparetidse and Amphictenidas. He is inclined to regard 

 it as a ductless gland of mesoblastic origin, and he suggests 

 its possible homology with the " notochord " of Balanoglossus. 



E. Meyer (24, B) describes the heart-body of Chsetozone 

 ssetosa, and expresses the opinion that its function consists 

 in the preparation of the pigment which is dissolved in the 

 red blood-fluid. 



Jourdan (17), in his work on Siphonostoma diplochaetos, 

 gives an account of the " caecum gastro-oesophagien,'' or heart- 

 body. He speaks of it as " communiquant avec le tube 

 digestif," which is denied by Bles (5), who supports the view 

 that the heart-body is of mesoblastic origin, remarking that 

 chloragogen is peritoneal, and that the connections of the 



' " Haemolymph " is the word used, but it evidently refers to the coelomic 

 fluid. Would it not be better to restrict the term " haemolymph " to such 

 fluids as represent the combined blood and lymph, such as that of the Capitel- 

 lidae, to which Eisig previously applied the word? It was first used by 

 Professor Ray Lankester for a fluid consisting, like Vertebrate blood, of both 

 "hsema" and "lymph," when discussing the presence of corpuscles in what 

 was then called the " pseud-hsemal " system of Chsetopods (this Journal, 1878). 



