138 Scientific Proceedings, Royal Dublin Society. 



Specimen 7 (Dalkey Island). — This specimen had two oeso- 

 phageal grooves and two pairs of directive mesenteries. Near the 

 oral disk twenty-nine pairs of mesenteries reached the oesophagus 

 — thirteen pairs on one side, between the oesophageal grooves, and 

 fourteen on the other. Alternating with these were twenty-nine 

 pairs of small mesenteries. Lower down, the number of mesen- 

 teries reaching the oesophagus was reduced to sixteen pairs. These 

 remained perfect the whole way down to the base of the oesopha- 

 gus. In this specimen also the oesophageal ribs corresponded to 

 the points of insertion of the mesenteries. 



Sagartia miniata, Gosse. 



The arrangement of the mesenteries was also made out in three 

 specimens of S. miniata, all obtained at Dalkey Island. Of these 

 three, two were rather small, while the third was an average- 

 sized specimen. 



Specimen a (Dalkey Island). — This specimen had no well- 

 marked grooves, but two pairs of directive mesenteries were plainly 

 visible. Altogether, six pairs and one odd mesentery reached the 

 oesophagus. The odd mesentery was situated next one of the pairs 

 of directives, with its longitudinal muscle turned in the same 

 direction as those of the mesenteries on each side of it. In each 

 intermesenteric chamber, except in that one in which the odd 

 mesentery was, a pair of very small mesenteries was present. Here 

 also the oesophageal ridges corresponded to the mesenteries reaching 

 the oesophagus. 



Specimen j3 (Dalkey Island). — This small specimen had a 

 single oesophageal groove and a single pair of directive mesenteries. 

 Seven pairs of mesenteries in all reached the oesophagus. 



Specimen 7 (Dalkey Island). — This specimen had a single 

 oesophageal groove, and a single pair of directive mesenteries. 

 Near the oral disk fourteen pairs of mesenteries joined the oeso- 

 phagus ; lower down the number was reduced to ten pairs. It was 

 only quite close to the oral disk that the oesophageal ridges were well 

 marked. There were a good many small mesenteries apparently 

 irregularly developed in the intermesenteric chambers. 



