The mesenterial Filaments of the Alcyonaria. 7 



locai thickening of the edge of the septura. It seems incredible that 

 the region betweeu the stomodaeal ectoderm and the filament consists 

 of ectoderm cells, derived from the former , which have lost their own 

 characteristics and completely assumed those of entoderm cells , and 

 this hypothesis is disproved by the following observations on Funiculina. 

 In fig. 13 the entodermic filameuts have not yet appeared in the 

 youngest bud, A. As in Älci/onium we can follow the stomodaeal ecto- 

 derm , V.W. down to the lip of the Oesophagus , where it becomes 

 continuous with the border of the ventral septum, v.s. The contrast 

 between the stomodaeal and the septal cells is of the same nature as in 

 Aloyonium^ though rather less marked. Beyond the lip we find only 

 entoderm cells , and the limit between the two kinds of cells is some- 

 times sharply defined. In the next older bud, B, we observe quite simi- 

 lar facts, but the edge of the ventral septum is slightly thickened at e.f. 

 some distance down the septum, and the nuclei are somewhat crowd- 

 ed. Fimilly, in the oldest bud, C, this thickening is more pronounced, 

 and is shown to be the filament by the fact that it already contains so- 

 lid food-})articles inclosed in vacuoles, v. (see the following account of 

 the functious of these filaments) . There is no evidence whatever of a 

 downgrowth of ectoderm cells, but the filament arises quite indepen- 

 dently of the stomodaeum. 



In Kophohelemnon ^ fig. 5, we find similar facts. In this case the 

 entodermic and ectodermic nuclei are ncarly of the same size but the 

 contrast between the stomodaeal and septal cells is rendered very dis- 

 tinct by the circumstance that the latter contain considerable quanti ties 

 of a yellowish pigment, in the form of small highly refringent pigment 

 granules , which is completely absent from the former. The rudiment 

 of the filament is shown at e./., at some distance from the Oesophagus, 

 and it consists entirely of entoderm cells. Below it, at o«., are two em- 

 bryonic ova. 



These observations, taken in connection with those on Renilla, 

 render it certain, I think, that the six short filaments have no- 

 thing to do with the stomodaeum and are strictly ento- 

 dermic s t r u c t u r e s . The region marked in . in fig. 1 J marks the 

 limit between the ectoderm and entoderm cells, and apparently consists 

 of partially or completely degenerated cells , originally derived from 

 the stomodaeum. 



c) Function. 

 Passing over the fantastic views of many early writers, we find 



