8 Edmund B. Wilson 



it to be uow genemlly recogiiised tliat the mesenterial filaments of po- 

 lyps in general play au important part in the functious of digestion — 

 though exactly how, and to what extent , has imtil very recently been 

 a matter of pure conjecture, owing to the great difficulty of observations 

 lipon living animals, and the lack of precise auatomical knowledge. 

 The brothersHERTWiG, after stiidying in the most masterly mauuer 

 the structure of many Actinians, carne to the conclusion tliat the mesen- 

 terial filaments of these animals are at least very important organs of 

 digestion ; but exactly how their functions are performed was not de- 

 termined, since their studies were anatomical rather than physiological. 

 Miich the most important evidence lipon the subject has been brought 

 forward by Kkukenbergi. His important conclusion, based lipon the 

 physiological study of a considerable number of Actinians, is that the 

 mesenterial filaments are not only uuquestionably Or- 

 gans of digestion, but they are the only organs of diges- 

 tion. His extensive experiments appear nearly or quite conclusive 

 upon this all-important point. He found, farthermore, that digestion 

 takes place only when the food comes into actual contact with the fila- 

 ments, and that during digestion the filaments are wound about the 

 food (»umstricken«). 



So far as I am aware, I was the first directly to observe the action 

 of the filaments during digestion, in the case of the Gorgonian Lepto- 

 gorgia virgulata Edw. and Haime -. A young transparent polyp was fed 

 with oyster eggs and observed under the microscope. The food was held 

 for two or three hours closely clasped by the mesenterial filaments 

 which were drawn closely together around the mass of 

 eggs in the upper part of the stomach. Afterwards, a mass of refuse 

 matter was passed out through the Oesophagus and the filaments re- 

 sumed their ordinary position. In this young polyp the dorsal filaments 

 were still rudimentary . So far as could be determined theentoderm 

 of the radial Chambers took no part in theprocess of di- 

 gestion, which was entirely performed by the six ento- 

 dermic filaments. This is entirely in accord with Krukenbekg's 

 studies upon the Actinians. 



Since these observations upon Leptogorgia (which have been long 

 delayed in press) A. Milnes Marshall and William P. Marshall 



1 Vergleichend-Physiologische Studien un den Küsten der Adria, I. Abthei- 

 luug, Heidelberg, 1880. 



2 Phil. Trans. 18S3, p. 64. 



