FORM REGULATION IN CERIANTHUS /KSTUARIl. 35 



tentacles began during the period of temporary distention, but 

 after collapse these tentacles atrophied and no trace of labial 

 tentacles ever appeared. Moreover the piece gradually under- 

 went decrease in size and atrophy and finally broke up and died. 



Piece II., on the other hand, gave rise to a normal animal 

 with both marginal and labial tentacles and remained in good 

 condition for months. 

 Scries jj. 



September /j, igoj. — Four oesophageal pieces from different 

 individuals, each including about the middle half of the oesopha- 

 geal region. 



September 20. — In all the oesophagus and body-wall have 

 united at both ends and the enteron is without communication 

 with the exterior. The pieces are slightly distended and one 

 shows slight elevations of the body-wall in the marginal tentacle 

 region ; the others are without any trace of marginal tentacles, 

 and none show any trace of labial tentacles. 



October 2. — All collapsed and reduced in size. No traces of 

 tentacles in any. In three pieces the body-wall has atrophied 

 and split along the line of longitudinal folds. 



Later History. — All four pieces gradually atrophied and broke 

 up and the fragments died. No further traces of tentacles ap- 

 peared at any time. During the same time other pieces of the 

 same and smaller size but with aboral ends proximal to the 

 oesophageal region, closed, became distended, gave rise to mar- 

 ginal and labial tentacles and remained in good condition until 

 the conclusion of the experiment on December 31, 1905. 



In general the development of marginal tentacles is almost 

 completely inhibited in cesophageal pieces and the tentacles which 

 do appear undergo complete atrophy later. Labial tentacles have 

 never been seen in the pieces. Moreover the pieces are incapa- 

 ble of continued existence for more than a few weeks in the 

 absence of internal pressure. 



(r) The Devclopuicnt of Tentacles on Oblique Oral Ends. 

 In C. solitarins the formation of tentacles on oblique oral ends 

 is not simultaneous about the whole margin as it is on transverse 

 ends, but the tentacles appear earliest on the most distal portion 



