ALCYONIUM 



109 





in such a way as to produce an upward current of water towards the 

 stomodaeum. In the case of the six other mesenteries the mesenterial 



eg. 



B 



coel. 



t 



FIG. 47. 



Alcyonium : transverse sections. A, through stomodaeum ; B, slightly below stomodaeum. 

 Ciliated groove ; M, mesenteries ; m, muscle ; A/./, mesenterial filament ; s, stomodaeum. 



lent is much folded, forming a little skein-like mass ; it extends 

 ily for a short distance down the free edge of the mesentery and 

 epithelial covering is 

 >wded with gland-cells, 

 secrete the diges- 

 i ferment. Below 

 level of the mesen- 

 ial filaments these six 

 jnteries show during 

 winter months little 

 mnded swellings near 

 free edge. These 

 sellings are the young 

 ovaries or testes, which 

 are consequently endo- 

 dermal in position as they 

 are in the Acalephae. 



The ectoderm covers FlG- 48 ' 



Portion of section through Alcyonium colony parallel to 



the OUter Surface Of the surface, coel, Coelenteron with the eight mesenteries, the two 

 dorsal ones showing mesenterial filaments (black) ; sp, spicules ; 



sp. 



polyp and of the colony 

 in general : the endo- 

 derm lines the coelen- 

 teric spaces. Between the two layers of cells are extensive regions filled 



st, strands and t, tubes of endoderm connecting the walls of the 

 various coelentera. The dotted groundwork of the figure repre- 

 sents the matrix of mesogloea. 



