526 



PROF. GILBERT C, BOURNE ON FIVE 



(left iu the figure) dorso-lateral megaccele the two micromesenteries adjacenh 

 to macromesenteries extend neavlj across the peristome to the actinopharyiix, 

 the two micromesenteries in the middle o£ the chamber are shorter, but that 

 on the dorsal side is markedly the shorter o£ the two. In the corresponding 

 megaccele on the left side of the body (right in the figure) there are six 

 micromesenteries, of which the two adjacent to the macromesenteries are the 

 lonoest, the two in the middle of the chamber are very short, and the two 

 others are of intermediate length. In each of the lateral and ventro-lateral 



Text-fisure 2. 



u 



5 



1. Oral disc of a specimen of Editardsia carnea, Gosse, ■uith 30 tentacles, eight macro- 

 mesenteries, and twenty-two micromesenteries. 



2-5. Diaorams of one of the dorso-lateral megaccele?, showing the probable order of 

 development of the micromesenteries and tentacles, a-d, micromesenteries lettered 

 according to their probable order of development ; 1-5, tentacles. 



megacoeles there are three micromesenteries, of which the two adjacent to the 

 macromesenteries are the longest, the middle one being distinctly shorter. 



It can hardly be doubted that the longer micromesenteries are the older, 

 the shorter the more recently formed. This rule holds good for all other 

 Actinians, and there are no grounds for supposing that the Edwardsiaj form 

 an exception to it. On the assumption that the rule is applicable to this 

 case, my interpretation of the facts is given in the series of diagrams of a 

 single megaccele (text-fig. 2, 2 to 5). 



