FORM-REGULATION IN CERIANTHUS. 



I 9 7 



In the third (delayed) piece the longest marginal tentacles on 

 the upper side of the disc are 89 mm. while on the extreme 

 lower portion only minute buds are present. Labial tentacles are 

 present on the upper half of the disc, the longest being 2-3 mm 



FIG. 5. 



In all cases the disc is becoming less oblique (cf. Figs. 5 and 6). 



Controls. A. Marginal tentacles S-io mm. about whole cir- 

 cumference. Labial tentacles somewhat irregular in length 1-4 

 mm. B. Marginal tentacles in one piece 8-9 mm., in other 5-6 

 mm. Labial tentacles in one piece 1-4 mm., in other about i mm. 



FIG. 6. 



Beyond this point the controls need not concern us. The ex- 

 perimental pieces were observed at intervals during three weeks 

 more. During that time there was little increase in length 

 of the longest tentacles, but the shorter tentacles continued 

 to grow until the asymmetry was only slight : in other words 

 the tentacles on the upper side of the disc completed their regen- 

 eration earlier than the others. Meanwhile the disc gradually 

 became less and less oblique until it too was almost symmetrical 

 in position. In all pieces the obliquity of the disc was much less 



