vol. i] Torrey— Mery. — Regeneration in Sagartia Vavisi. 



213 



1. Tin' first method to be considered may be characterized .-is 

 aboral-oral fission by constriction and rapture, with subsequent 

 repair. 



(>t) Fission. The first signs of division appear in the re 

 arrangement of the mesenteries <>n the semi-transparent fool disk, 

 and the elongation of the latter along a line parallel with the 

 major axis of the mouth by the active locomotion of two opposite 

 regions away from each other. The typical arrangement of the 

 mesenteries is strictly radial, around a single center. When 

 division begins, the original center gives way to two (Fig. 1). 

 which move farther and farther apart as division progresses. 



A glance at Figs. 2 and 3 may make clear what is very 

 apparent in the foot disks from which they were drawn, that the 

 divergence of the centers is accompanied by a tension, which 

 particularly affects the region between them, and is indicated by 

 the course of the mesenteries. The boundary between foot and 

 column, never sharply marked, becomes less and less distinct, 

 especially in the narrowed intermediate region between the 

 incipient foot disks of the future daughter polyps (Fig. •'!). 



Fig. 3. Foot disk of dividing polyp; a later 

 stage than th.it shown in Fig. 2. From below. 



Fig. 4. Foot disk of a dividing polyp, 

 showing rupture. From below. 



As a result of the tension, the attenuated tissue on the foot 

 disk between the centers is ruptured before lone-, and a gaping, 

 diamond shaped wound is formed (Fig. 4). From this point, 

 the division runs rapidly to completion. The diamond increases 



