vol.. i.] Torrey-Mery. — Regeneration in Sagariia Davisi. 219 



with that early stage of fission of the first type which imme- 

 diately preceded a tear (Pigs. 2, 3). The condition represented 

 in it may be readily derived from a, and there is evidence thai 

 it is so derived. For the condition represented bj & has been 



seen to merge into th adition represented by a as a result of a 



separation of the two foot disks and a consequent stretching of 

 the intermediate tissue. We think it highly probable that dur- 

 ing a period of comparative inactivity in such a case as <t, two 

 fool disks have been differentiated from the tissue of the isthmus 

 com ting them, this isthmus being formed largely if not exclu- 

 sively by tissue of the body wall (cf. Fig. 3.) 



The best evidence, however, is to he obtained from the actual 

 division of one polyp, abnormal, it is true, but doubly interesting 

 on that account. This polyp was abnormal in that it possessed 

 a second mouth and set of tentacles on the side of the column. 

 It was unique in this respect among the many hundreds of polyps 

 we have examined; and since budding is unknown in the species, 

 we are disposed to believe that the supernumerary structures 

 were produced as the result of a wound on the column ; that they 

 can be so produced experimentally will be shown later. 



When the abnormal polyp was first observed, no signs of 

 division were noticed in the foot disk. A few days later the 

 mesenteries on the foot disk were seen to be arranged around 

 two centers. The foot disk had lengthened along the hue 

 passing through both centers. Two foot disks were soon distin- 

 guishable, separated by a constriction which proceeded slowly 

 upward. Without sign of rupture, a complete division was 

 finally effected. Instead of passing as usual across the mouth 

 disk, however, the fission plane passed between the tiro month 

 disks, a peculiarity for which the presence of the supernumerary 

 mouth and tentacles must be in some way accountable. The 

 direction of the fission plane with respect to the major axis of 

 either mouth was not observed, so that it still remained to be 

 determined whether or not the doubling of the mouth disks, 

 besides modifying to some extent the direction taken by the 

 fission plane, might not also have precipitated the division. By 

 way of solution, wounds were made in the columns of a number 

 of polyps in whose foot disks there were no sio,-iis of division. 



