F. Dixon — Mesenteries in the Genus Sagartia. 139 



Sagartia nivea, Gosse. 



In two specimens of S. nivea, obtained at Dalkey Island, 

 although the exact arrangement of the mesenteries was not made 

 out, it was certain that in one, at least, sixteen pairs were perfect 

 throughout the whole length of the oesophagus, and in the other 

 twelve pairs. Each had but a single pair of directive mesenteries. 



In a third specimen from Dalkey Island, which also possessed 

 a single groove and a single pair of directive mesenteries, twenty- 

 five pairs of mesenteries reached the oesophagus near the oral disk ; 

 alternating with these were twenty-five pairs of small mesenteries. 

 The arrangement of the mesenteries in this specimen was quite 

 similar to that in the first specimen of S. venusta, described above. 



Sagartia rosea, Gosse. 



I have had an opportunity of examining a single specimen of 

 this Actinia, which was kindly sent to me from Valentia by Mr. 

 W. De Y. Kane. It had but a single oesophageal groove, and a 

 single pair of directive mesenteries. In it twelve pairs of mesen- 

 teries were perfect throughout the whole length of the oesophagus. 



Professor E. Hertwig [(1882) "Challenger" Eeport on Acti- 

 niaria, p. 70] states of the Sagartidce, that they all possess acontia, 

 and that in all of them six pairs of principal mesenteries alone are 

 perfect, none of the others reaching the oesophagus. He goes on 

 to say that in no instance where acontia are present is the differen- 

 tiation of mesenteries wanting. The only exception to his defini- 

 tion of the family of which he takes any notice is S. troglodytes, 

 which, he says, Heider had described as having forty-eight pairs of 

 perfect mesenteries. This exception he explains away by attribut- 

 ing it to Heider's having mistaken sections through the oral disk for 

 sections through the oesophagus. Having thus got rid of the only 

 exception which he knew where the mesenteries did not conform to 

 what he called the typical Sagartid arrangement, Professor Hertwig 

 confirmed himself in his opinion by remarking that the family 

 Sagartidce, as he had defined it, would correspond, on the whole, 

 with Gosse's Sagartidce. 



