THE ANTHOZOA 



is weak, the longitudinal muscles being less developed than the 

 transverse, and there are no muscle banners. Carlgren (14) has 

 shown that the longitudinal muscles are always found on the same 

 face in each mesentery, namely, on the face turned away from the 

 ciliated groove. In Edwardsia the opposite is the case, and it 

 is concluded that the ciliated groove of Cerianthus does not 



FIG. XXV. 



1. rc.rianthus solitaries, Rapp. 



2. Transverse section through the stomodfeal region of Cerianthus, showing the sulculus, s, 

 and the arrangement of the mesenteries. (After O. and R. Hertwig.) 



3. Portion of a mesentery of Cerianthus membranaceus, showing the transverse muscles, 

 tm, the filament /. The Acontia-like threads, th, borne by the upper edge of the mesentery, 

 and g, the gonads. (After O. and R. Hertwig.) 



4. Section through the peristome of Cerianthus membranaceus, showing the longitudinal 

 ectodermic muscles, M ; ec, ectoderm ; mg, mesogloea ; en, endorterm. (After O. and R. 

 Hertwig.) 



5. Oral aspect of a young Arachnactis brachiolata, the larva of a Cerianthus, with seven 

 tentacles. (After E. van Beneden.) 



6. Transverse section through the stomodfeal region of an older larva. The numerals 

 indicate the order of development of the mesenteries. (After Boveri, slightly altered.) 



correspond with that of Edwardsia, but is the sulculus, the sulcus 

 being absent. 



The pelagic larva shown from the oral surface in Fig. XXV. 

 5 is known as Arachnactis brachiolata. It is the young form of 

 an undetermined species of Cerianthus. Fig. XXV. 6 is a trans- 

 verse section through the stomodaeal region of an older larva. It 

 has nine tentacles one small, median, and, according to Carlgren's 

 orientation, ascular ; six large and lateral ; two of unequal size, 

 but smaller than the lateral tentacles, occupy the sulcar region. 

 The section shows that these correspond to as many intermesen- 



