COMPAEATIVE ANATOMY OF SOME BRITISH ACTINI.T.. 



547 



of the stem contains nematocysts, but they are not so numerous as on 

 the tip. The nematocysts in the endoderm are not so numerous as those 

 in the ectoderm, and none are present in the endoderm near the base 

 of the tentacle. They are also present in the oval swelling at the tip of 

 the mesenterial filaments. The stomatodaeum is oval in section and the 

 wall is thrown into numerous deep and regular longitudinal folds. As 

 in C. myrcia, these folds show a rough approximation to the points of 

 attachment of the complete mesenteries. The ectoderm contains a large 



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Fig. 13. — Corynaetis viridis. Vertical section through the 

 body-wall, showing the sphincter muscle. 



number of gland cells, and near the base of this layer there is a quantity 

 of granular material. The mesogloea is thin except at the summit of 

 the folds, where it is thick and gives off small branches which form a 

 strong ectodermal muscle. The endoderm is spongy as in the column 

 wall, it is thicker than the mesogloea and contains large gland cells. 

 One gonidial groove is present, which is not very deep. 



The number and arrangement of the mesenteries vary in different 

 specimens. Transverse sections of three different specimens were cut. 

 In one there are 48 mesenteries, some complete and some incomplete, 



