L'lfi University of California 1 ublications in Zoology. I 



Vol. 6 



thai when the angle was greater than forty to forty-five degrees, 

 the tentacles almost invariably appeared parallel to the wound. 

 the center of the latter marking the tip of the proboscis. The 

 hydranth remained tilted on the stem to the rod of the experi- 

 ment, at which time it was well formed and symmetrical, though 

 the tilt was always less evident in the extended than in the 

 contracted polyp. 



When the angle was less than about forty degrees, the ten- 

 tacles appeared in circlets in planes approximately perpendicular 

 to the axis of the stem (as though the cut had been at an angle 

 of ninety degrees), or somewhat tilted from the perpendicular, 

 but away from instead of toward the wound. In fig. 1, both 

 the distal and proximal tentacles appear above the lower limit of 

 the wound, around an axis passing through the point of the stem, 

 and therefore in a plane not quite perpendicular to the old stem 

 axis. For a time the axis of the new hydranth in this ease was 

 not parallel with the stem axis. In two days, however, new 

 tentacles had grown on the sear, all inequalities had vanished, 

 and the remodelling of the stem as a whole had made the two 

 axes coincident. This was the final result in all cases observed. 



The position of the tentacles with reference to the obliqueness 

 of the wound will be discussed further in connection with the 

 subject of multiple monsters. 



2. Development of the Holdfast. 



The root filaments, or frustules, that form the holdfast, 

 develop throughout the life of the polyp. The details of their 

 development, their position, histology, and the factors determin- 

 ing their form, have been treated in the preceding papers of this 

 series, to which the reader is referred- The account there given 

 will answer with but slight amendments for regenerating stems. 



In the normal adult, the frustules occupy a zone girdling the 

 column near its proximal end. and arise progressively toward the 

 distal extremity. Proximally they are oldest and most com- 

 pletely functioning, becoming gradually less mature toward the 

 distal boundary of the zone, where they may be said to be in a 

 resting stage. Normally, their development is accelerated by 

 the development and disintegration of the frustules proximal to 



