No. 3-] THE MORPHOLOGY OF THE ACTINOZOA. HJ 



mens of which I found in a collection from the West Indian 

 seas made by the Bahama Expedition of the State University 

 of Iowa. I have been able to compare the specimens with 

 some kindly sent me by the U. S. Fish Commission; and in all 

 have examined seven specimens, each of which showed abnor- 

 mal arrangements of the mesenteries. Three cycles of mesen- 

 teries occur, the members of the first cycle alone being perfect; 

 and the third cycle is sometimes incomplete. I give below in 

 tabular form a statement of the arrangement of the perfect 

 pairs of mesenteries in each specimen, those pairs which are 

 directives being indicated by the letter D. 



Specimen No. i D 2 D 4 5 6 

 No. 2 D 2 D 4 D 6 

 No. 3 D 2 D 4 D 6 7 

 No. 4 D 2 D 4 D 6 7 

 No. 5 D 2 D 4 5 D 7 8 

 No. 6 D 2 D 4 5 (?) D 7 8 

 No. 7 D 2 D 4 D 6 D 8 



In drawing up this table I have in all cases started with a 

 directive, though it is of course impossible to say that in each 

 case the tabulation has commenced with the same mesentery. 

 Specimen No. 6 was received from the U. S. Fish Commission, 

 the rest are from the Iowa University collection. 



It will be seen from this table that of the seven specimens 

 two are arranged on the hexamerous plan, two on a heptamer- 

 ous plan, and three on an octamerous, though with regard to 

 specimen No. 6 it is not quite certain whether the pair num- 

 bered 5 belongs to the first or second cycle, its relations to 

 adjacent second and third cycle mesenteries indicating, how- 

 ever, its probable membership in the first. Furthermore it 

 will be noticed that in one specimen there are two pairs of 

 directives, which, however, are not opposite each other but are 

 separated by only a single pair of the first cycle ; in five speci- 

 mens there are three nairs of directives, and in one specimen 

 four. It is possible that specimen No. I should be credited 

 with three pairs of directives, since there is some uncertainty 

 concerning the pair of mesenteries numbered 5, one member 



