Factors of Form Regulation in Harenactis Atteniiata 481 



gives rise to a ring without any opening between the enteron and 

 the exterior (except of course the cincHdes), without any oral and 

 aboral end — since these two ends have fused, and in fact without 

 any of the features of shape and relation of parts characteristic 



of the species. There is no difficulty in obtaining these pieces. 

 They result almost invariably when the conditions described 

 above are established. Their further history is of great interest 

 but will be considered in another connection. Extrusion of the 

 oesophagus sometimes occurs in short pieces from the oesophageal 



region (e.g., between a and h. Fig. 2). If the extruded structures 

 are cut away rings are formed as in the cases just described and 

 for the same reason. 



The relation between the mesenteries and closure of the wound 

 in Harenactis does not differ very widely from that existing in 

 Cerianthus (see Child '04a, wound-closure after different kind 



