Factors of Form Regulation in Harenactis Attenuata 493 



TABLE I 



Time of appearance and length of tentacles in mm. at (liferent levels 



3 DAYS 



8 DAYS 



14 DAYS 



26 DAYS 136 DAYS 



I {a, Fig. 2) 1-2 



II (fe, Fig. 2) I 0.5 



III (c, Fig. 2) o. 



IV (<f, Fig. 2) I o. 



V (/, Fig. 2) I o. 



degenerating 



Table I gives the results obtained in five series of three pieces 

 each. The level of the oral end of each series is indicated in the 

 table by the reference to Fig. 2. In all cases the pieces include 

 all that portion of the body proximal to the level of the section, 

 consequently they are of very different sizes: in Series I, for exam- 

 ple they include practically the whole body except the extreme 

 oral end, and each of the follow^ing series includes less of the body 

 than the preceding until in Series V only the attenuated aboral 

 end is included, and the pieces arq only a small fraction of the 

 size of Series I. The tentacle measurements given in the table 

 are maximum and minimum measurements for all pieces of the 

 series: the tentacles of a single piece are usually very nearly equal 

 . in length. In Series IV only one piece out of three closed and 

 produced tentacles: in Series V two pieces closed but only one pro- 

 duced tentacles. 



As regards the time of appearance of the tentacles, the table is 

 not exact since the pieces were not examined every day, but it 

 shows clearly enough that the length of time between the opera- 

 tion and the appearance of the tentacles increases with increas- 

 ing distance of the level of section from the oral end. That the 

 presence or absence of the oesophagus is not responsible for this 

 difference is evident from the fact that a difference exists both 

 between levels within the oesophageal region (Series I and II) 

 and between those entirely aboral to the oesophageal region (Series 

 IV and V). 



The tentacles in all series attained their maximum length in 

 fourteen to twenty-six days after the operation. As a matter of 



