THE ANTHOZOA 



39 



tentacles. They are arranged in couples/ the members of each 

 couple being recognisable by the arrangement of their longitudinal 

 retractor muscles. These are attached to plaited folds of the 

 mesogloea and form the so-called muscle banners. They are so 

 disposed that the muscle banners of each mesenterial couple are 

 Ws a vis, with the exception of two mesenterial couples situated 



ic .y 



,. ■■;.-: *• " 



, -.^ci/. 



^#1' 



5. 4 



Fig. XIX. 



1. ^Diagrammatic longitudinal section through an Aetinian, Actinauge Richardi, to show the 

 general anatomy of the zooid. bir, body wall ; st, stomodaeum ; s, sulcus ; p, peristome ; mm, 

 mesenteries ; 7)i/, mesenterial filament. (After Haddon.) 



2. — A mesentery of Tealia crassicornis. t, tentacles ; g, gonads ; r, Rotteken's or circular 

 muscle; si, internal; and se, external stomata ; ?»/, mesenterial filament; Im, longitudinal 

 retractor muscle ; pUm, parieto-basilar muscle. (After O. and li. Hertwig.) 



3. — Transverse section between two couples of primary mesenteries of Adamsia RondoMii. 

 1, 2, 3, 4, and 5, primary, secondary, tertiary, quaternary, and quinary mesenteries, lin, muscle 

 banners ; g, gonads. (After O. and R. Hertwig.) 



4. — Transverse section through the stomoda?al region o{ Adamsia diaphana. s, sulcus; si, 

 sulculus ; dd, the two couples of directive mesenteries. (After O. and R. Hertwig.) 



i>. — Si'ction through mesenterial filament of Actitiia equina, enl, cnido-glandular lobe ; dl, 

 ciliated lobes. The animal had been fed with powdered carmine, the particles of which have 

 been ingested by the cells lying between the cnido-glandular and ciliated lobes, and are repre- 

 sented by the black masses. (Original.) 



at the two ends of the long axis of the stomodaeum. In these, 

 which are called the directive mesenterial couples, the muscle 

 banners are turned away from one another. 



Mesenteries are complete or incomplete. A complete mesentery 

 is attached by the upper part of its inner margin to the stomodaeum, 

 an incomplete mesentery is not. The free edge of each mesentery 



^ It is convenient when speaking of the adult arrangement of the mesenteries to 

 use the word "couple," when of their developmental sequence to use the word "pair." 



