12 

 \i I 

 3, 13, Z 



3, 



Experiments on Polarity in Tiihularia. 573 



Experiment 5. The rate at which the hydranth forms is, 

 it appears, an important factor in connection with the phenom- 

 enon of heteromorphosis. A series of experiments was under- 

 taken to determine whether the amount of material in the 

 circulation has an influence on the rate at which the hydranths 

 appear. This and the five following experiments have a bearing 

 on this point. 



In several series a long piece was cut out and its ends allowed 

 to close. Then at intervals small pieces were cut from the 

 aboral end. Each time that a small end-piece 

 is removed a part of the circulating fluid with 

 its contained granules escapes from the long 

 piece into the water. The cut end closes in the \ 



course of an hour making further escape of fluid 

 impossible. It is true that a small amount of 

 new material is added from the ridges at the 

 aboral end each time the piece is cut, but it 

 appears that not enough is added to compensate 

 for that which is lost. The greatest amount of I [ 



pigment, etc., always comes from the endoderm table VIII. 

 of the oral end where the changes preparatory 

 to the formation of a hydranth takes place. The following are the 

 records of the results. A check series of pieces, not cut at intervals 

 at the aboral end, was kept in each experiment. In one set the 

 long pieces were cut at 10.00 a. m., July 15, and at 3.00 p. m. 

 the aboral ends were cut off. The next morning (July 16, 

 9.45 a. m.), 18 of these pieces showed the primordia of tentacles, 

 two had none. The check pieces were in the same condition. 

 At 4.10 p. m. none of the polyps was out. The next morning 

 (July 17, 9.00 a. m.) 11 hydranths were out, 6 showed the 

 primordia of polyps, one nothing. Of the check series, 9 polyps 

 were out, and 3 pieces showed primordia. The following morn- 

 ing 16 polyps were out, and 2 not yet out; of the check set 10 were 

 out and 3 not yet out. 



In another set (July 31) the pieces were cut off^ at 11.30 a. m. 

 The first aboral cut was made at 5.50 p. m., and the second the 

 next morning at 9.00 a. m. At this time the beginning of the 



