FORM REGULATION IN CERIANTHUS .KSTUARII. 



43 



Other part except at its proximal end where it is continuous with 

 the rest of the body-wall. Thus the closure of the wound re- 

 sults in the formation of a small component extending obliquely 

 in the distal direction from the side of the body. The cesophagus 

 also closes longitudinally in each part and in the lateral compo- 

 nent unites distally with the body-wall so that this component 

 possesses a mouth. In this manner an oblique lateral disc is 

 established at the distal end of the lateral component, but it is a 

 complete not a partial disc, because the closure has been largely 

 longitudinal. On such discs the tentacles arise in the manner 

 characteristic for oblique discs, i. e., earliest on the most distal 

 portion and latest on the proximal portion of the disc (Fig. i8). 



18 



In Fig. 19 one of these cases is shown after complete devel- 

 opment of the tentacles on the lateral disc, but before the obli- 

 quity has disappeared. In this figure it is seen that several of the 

 tentacles on the original terminal disc, viz., some of those which 

 were situated directly distal to the incision, have undergone par- 

 tial atrophy. The stage figured does not, however, represent the 

 greatest degree of atrophy which occurred. After the closure 

 of the wound these tentacles underwent rapid atrophy until they 

 were reduced to less than half the length shown in the figure 

 and some of them were mere stumps 2-3 mm. in length. Then 

 they began to grow again and would undoubtedly have finally 

 attained the same length as the others if it had been possible to 

 continue observation of the specimen for a longer time. The 

 reason for the peculiar history of these tentacles is to be found 

 in the method of closure of the wound. In Fig. 17 the direc- 



