PEDAL LACERATION IN ACTINIANS. 85 



The young actinian shown in Fig. 6 has already acquired the 

 characteristic appearance of all small specimens of this species, 

 so that, from an external examination, it would be impossible to 

 determine whether it had come directly from an egg or from a 

 laceration piece. As compared with any of the figures of earlier 

 stages the proportionate diameter of the column is very much 

 reduced. This has been brought about by a continuation of the 

 same processes that are shown at an earlier stage in Fig. 3. The 

 basal portion of the column is now of no greater diameter than 

 the upper part, while the whole animal has become considerably 

 elongated. The first eight tentacles are now of practically the 

 same length as are also the eight pairs of secondary tentacles. 

 Internally the stomodeum can be seen to have increased greatly 

 in length. The mesenteric filaments, not previously distinguish- 

 able, have now become very prominent structures on the first 

 eight mesenteries. The column wall has become thin and has 

 lost its pigment clear to the base through which are seen the points 

 of insertion of the first eight mesenteries, while those mesenteries 

 that came over from the parent actinian in the laceration piece, 

 have entirely disappeared, even at the extreme base of the young 

 specimen. 



In following through the development of any single laceration 

 piece from the time of its separation from the parent until it 

 becomes a typical young actinian it is apparent that there has 

 been very little, if any, increase in its bulk, and that the change 

 in shape has come about almost entirely through the readjust- 

 ment of the materials already present and not to any considerable 

 extent through the metabolism of new material. 



Frequency of Reproduction by Laceration among the 



Forms Studied. 



The following table shows the frequency of this method of 

 reproduction among the four species studied and the number of 

 young that has arisen from a single parent individual within 

 a given time. 



In another instance many thousand individuals of A. pallida 

 were examined casually, but without any records being kept, 

 and here again it was found that the percentage of those which 



