FORM-REGULATION IN CERIANTHUS. 2OQ 



closed while no longer than these and differing from them only 

 in that the oesophagus communicated with the enteron, regener- 

 ated marginal tentacles 8-10 mm. in length and labial tentacles 

 5-6 mm. and produced new tissue at the aboral end. 



Scries 32. 



October i, 1902. Seventeen oesophageal pieces were pre- 

 pared (Fig. 7) the distal cut being in this case slightly more 

 aboral than in Series 30 (Fig. 15) so that both marginal and 

 labial tentacles and most of the surface of the disc were removed. 



During two weeks these were examined several times. In all 

 pieces the cut margins of oesophagus and body-wall united both 

 orally and aborally and in none did the closure of the body-wall 

 across the aboral end occur. All of the pieces became slightly 

 distended during the first few days and marginal tentacles ap- 

 peared as minute buds less than i mm. in length. In no case did 

 regeneration proceed beyond this stage : labial tentacles never 

 appeared. At the end of two weeks some pieces were beginning 



to break up. 



Series 4.7. 



November 7, 1902. Nine oesophageal pieces were prepared 

 in the same manner as those of Series 32. 



November 10. 3 days after section. Still more or less com- 

 pletely collapsed : no tentacles visible on any. 



November 12. 5 days after section. One piece closed abor- 

 ally, and well-filled with water; marginal tentacle-buds 0.51 

 mm. In the remaining eight pieces oesophagus and body-wall 

 have apparently united both orally and aborally : these pieces 

 are only slightly distended and show a slight crenation of the 

 oral margin corresponding to the intermesenterial chambers. 



November 20. 13 days after section. During the interval 

 since the last examination seven pieces closed aborally across 

 the end of the oesophagus. These are fully distended and bear 

 marginal tentacles 23 mm.; labial tentacles just appearing. 



In two pieces the oesophagus remained open aborally. These 

 are not fully distended and the marginal tentacles are minute 

 buds about 0.5 mm.; labial tentacles are absent. 



December 2. 23 days after section. In the seven closed 



