Rcaoicrafioii in Hydroincditsac 9 



ExPERiMi:xT 25. — Tiibularia tcncUa was cut into pieces of 12 

 to 20 mm. and arranged as in experiment 24. In about 48 hours 

 several pieces showed the formation of one line of tentacles. The 

 development then proceded rather slowly, hydranths being formed 

 gradually. The process of development of hydranths differs 

 somewhat from that in T. crocca. The end closes over in about 

 the same way, circulation of fluid begins, and red pigment is 

 deposited in the hydranth region. Then instead of the forma- 

 tion of the tentacle anlagen the hydranth body is separated from 

 the rest of the stem by a constriction (fig. 140). The tentacles 

 appear not as ridges, but as small buds (figs, i^h, 14c), and the 

 hydranth is pushed out of the old perisarc (figs, i^d, h/)- The 

 tentacles continue to grow until they reach their normal length. 



Experiment 2"/. — Tiibuloria larynx. — The pieces were cut in 

 about the same lengths and arranged in the same manner as in 

 the previous experiments. In 24 hours only one piece showed 

 the presence of "tentacle anlagen (this was at 8:00 p.m.)- The 

 next morning nine or ten fully formed hydranths were found. 

 The next day all that had not yet developed hydranths were 

 found to have formed them. (However, several pieces from the 

 extreme basal region did not regenerate at all during the progress 

 of the experiment j. Most of the pieces had hydranths at each 

 end, and there seemed to be a strong tendency to form in this 

 way ; moreover, there was no noticeable difference in the time 

 o'f development of hydranths of either end. All the hydranths 

 were cut off. In 24 hours all showed the tentacle anlagen, anci 

 a little later hydranths were fully formed. One piece which had 

 regenerated a hydranth cast it and formed another. This one 

 was removed and another developed. This one was also cut oft", 

 and still a new one regenerated. Thus in just a week one piece 

 regenerated four hydranths one after the other, the last three 

 being formed in four days. vSince I was forced to leave \\'oods 

 Hole at this time, the regeneration of this piece could be fol- 

 lowed no further. 



In this species the regeneration differs from that of T. crocca 

 and T. tcnclla. In every case under observation the first sign 

 of regeneration was the emergence of the coenosarc from the 



2S3 



