F. Dixon — Mesenteries m the Genus Sagartia. 137 



This is merely a preliminary notice ; and I hope to be able, at 

 a future date, to lay before the Society an account of the arrange- 

 ment of the mesenteries in these Actiniae at different ages, and 

 thereby possibly to throw some light upon the apparently anoma- 

 lous facts here recorded. 



I am indebted to Professor Haddon for much valuable assist- 

 ance in making these investigations, which, by his kind permission, 

 were carried on in the Zoological Laboratory of the Eoyal College 

 of Science, Dublin. 



Sagartia venusta, Gosse. 



The arrangement of the mesenteries was examined in three 

 specimens of Sagartia venusta, two of which were collected by Pro- 

 fessor Haddon, at Valentia, county Kerry, while the third was 

 obtained by myself at Dalkey Island, county Dublin. 



Specimen a (Yalentia). — This specimen had but a single oeso- 

 phageal groove and a single pair of directive mesenteries. The 

 groove was much more marked in this than in either of the two 

 following specimens. Near the oral disk twenty-five, or perhaps 

 only twenty-four pairs of mesenteries reached the oesophagus. 

 Alternating with these were twenty-five pairs of very minute 

 mesenteries. Lower down the number of mesenteries reaching 

 the oesophagus was reduced to twelve pairs, these twelve remaining 

 perfect to the base of the oesophagus. 



Specimen j3 (Valentia). — This was the only specimen in which 

 the arrangement of the mesenteries was quite regular. There 

 were two oesophageal grooves, and two pairs of directive mesen- 

 teries. In the neighbourhood of the oral disk twenty-four pairs of 

 mesenteries reached the oesophagus, in the spaces between which 

 were developed twenty-four pairs of small mesenteries, and alter- 

 nating with these and those reaching the oesophagus were forty- 

 eight pairs of still smaller ones. Lower down, the number of 

 mesenteries reaching the oesophagus was reduced to twelve pairs. 

 These remained perfect throughout the whole length of the oeso- 

 phagus. In this specimen the oesophageal ridges plainly corre- 

 sponded to the points of insertion of the mesenteries. 



