574 T. H. Morgan and N. M. Stevens. 



polyp could be faintly seen. At lo.oo a. m. on the following 

 day (August 2), 6 polyps were out, i was coming out and i showed 

 nothing. Of the check set, 4 were out and i had the primordia 

 present. 



In a third set the pieces were cut out at 10.45 ^' "^-j J^^Y 3*^- 

 The first aboral cut was made at 2.35 p. m., the second at 6.00 

 p. m., and the third the next morning (July 31) at 9.40 when 

 the primordia were present. After another 24 hours (August i, 

 9.45 a. m.) the polyps were all out in the normal time. These 

 results show that by opening the stem and allowing the escape 

 of fluid, the development of the polyp is not retarded. 



Experiment 6. In two experiments short pieces were cut from 

 the oral end at the same intervals as in the last series; Experi- 

 ment 5. This operation suffices to let some of the fluid and the 

 collection of pigment escape. The polyps were slightly retarded 

 (emerging at 3.00 p. m., August i), which is not surprising when 

 it is recalled that the cuts removed a small portion of the distal 

 end of the hydranth. 



In another series the pieces were cut off" July 14, at 2.30 p. m., 

 the first oral cut made at 6.00 p. m., and the next day (July 15) 

 two cuts were made at 10.00 a. m. and 3.00 p. m., respectively. 

 The following morning (July 16, 9.30 a. m.,) another cut was 

 made when the primordium of a polyp was present on 4 pieces. 

 The check pieces were in the same condition. The polyps did 

 not emerge until July 17, when proportionately as many were 

 out as in the check series. There was a slight delay caused by 

 the cutting, owing no doubt to too much of the polyp being re- 

 moved, but since the primordia formed at the same time as in the 

 check series, it is clear that the development up to this stage was 

 not delayed by removing very short pieces of the oral end of the 

 stem at four diff'erent times. Very small pieces only should, 

 of course, be removed, for if a longer piece is removed, the region 

 of tentacle formation is cut through, which will cause a delay 

 in subsequent development. The most distal part of the hy- 

 dranth-forming region goes to make the proboscis and may be 

 removed in the early stages without interfering seriously with 

 the development of the hydranth. 



