FORM REGULATION IN CERIANTHUS. 319 



of the experiment. Examination of the data shows that the 

 pieces B were all filling with water eleven days after section ; that 

 two days later all but four were collapsed, and that, finally, 

 seventeen days after section, only one piece was filled with water. 

 These changes are undoubtedly due to the fact that the growth 

 of new tissue at the ends of these pieces failed to keep pace with 

 the pressure of water in the enteron, and so rupture occurred as 

 soon as the pieces reached a certain point. In only one case 

 did the new tissue remain intact, viz., the case in which tentacles 

 appeared. 



As is evident from a comparison with other series, viz., series 

 22, 35, and 45, regeneration was found to occur in other cases in 

 pieces representing about the aboral third of the body, though 

 pieces representing the aboral fifth (series 45) or less did not 

 regenerate. Why then did regeneration fail to occur in the 

 aboral pieces of the present series ? The difference is un- 

 doubtedly to be accounted for by the low temperature of the 

 water. This series was begun in December and continued into 

 January. The temperature of the water was very much lower at 

 this time than during the autumn, and several other series begun 

 on the same date showed similar results. In other words, the area 

 at the aboral end which is incapable of regeneration increases 

 as the temperature becomes lower, and in the present series in- 

 cludes more than the aboral third of the body. This point will 

 be discussed in a following section where the influence of tem- 

 perature is considered. 



( To be Continued.} 



