■_ >- jo University of California PuMications. [zooloot 



Simple cuts and punctures healed readily without the production 

 of new structures. When pieces were cut out of the body wall, 

 and the fusion of the edges of the wound was thus hindered, 

 1 icttcr results were obtained — six double-headed polyps in all. 

 None of these showed any tendency to divide in any way, though 

 they were watched for three weeks. This result looks like a 

 demonstration of the view that division is not initiated by a 

 doubling of mouth and mouth disk, and is consequently little 

 less than a demonstration of the norma! occurrence of fission by 

 constriction in 8. davisi. We shall repeat the experiments ou a 

 larger scale. 



II. CAUSES OF FISSION. 



Fission of the first two types in 8. davisi depends to such a 

 degree upon active movements of different areas of the foot disk 

 in opposite directions that the idea readily suggests itself that 

 the establishment of some sort of physiological discontinuity 

 between these areas may lie the key to the causal problem. A 

 solution was attempted bj experimentation. 



Two sets of experiments produced slightly varying results. 

 In the first set, twelve polyps were cut from foot half way to 

 mouth, the cut being perpendicular to the major mouth axis 

 {i.e., parallel with the course of a normal fission plane) ; one had 

 divided in six days, two more in twelve days. Eight polyps 

 were cut from mouth half way to foot, also perpendicular to 

 major mouth axis; two had divided in three days. In the 

 second set, eight polyps were cut from mouth half way to foot, 

 parallel with major mouth axis. In one of these, the wound was 

 repeatedly reopened, but healed again in every case, and no divi- 

 sion resulted. Three polyps were cut half way to foot disk, 

 across the major mouth axis; no division resulted. 



Six polyps were cut from foot half way to mouth, across 

 major mouth axis; in twenty-four hours three had divided. It 

 was found also that if a polyp which is beginning to divide be 

 cut parallel with major mouth axis half way to the foot, the 

 division is inhibited until the wound is healed, and if the latter 

 is reopened, as was done repeatedly in one case, the division 

 takes place only after the wound has finally closed. 



