No. 569] 



BEGENEBATION 



293 



teen days and was in bad condition when examined. The 

 stomach had begun to expand and retractor muscles were 

 present. Probably owing to the condition of the speci- 

 men, no calcareous ring, ring canal, or Polian vesicle 

 could be found. Another individual killed at about fif- 

 teen days showed the stomach slightly enlarged, and the 

 intestine, retractor muscles, calcareous ring, tentacular 

 canals, and ring canal well formed. Two small Polian 

 vescicles each about one millimeter in length were pres- 

 ent. The position of the new intestine was described in 

 my notes as follows : 



From the stomach the intestine follows the ventral edge of the dorsal 

 trally with the mesentery and then forward for about one half inch to 



ventral part of the cloaca. 



At a little later stage in another specimen the intestine 

 passed from the left ventral interradial to the right ven- 

 tral interradial space ; then posteriorly and again to the 

 left, following the ventral radial mesentery to the ante- 

 rior ventral side of the cloaca. 



We see from the preceding description that all impor- 

 tant organs have been reproduced in form though not in 

 size, before the end of the fifteenth day. The first madre- 

 porite with its tiny stone canal was found some eighteen 

 days after mutilation. Twenty-one days after eviscera- 

 tion in one specimen the calcareous ring was about three 

 millimeters in diameter and the ampullar at the bases of 

 the tentacles were well developed. Within a week after 

 this time the regenerating animal begins active feeding. 

 Thyone A, killed at 41 days, was practically a normal 

 animal both in behavior and appearance, except for the 

 fact that the regenerated organs had not yet reached full 

 size. The stomach was about one third normal size, but 

 the Polian vescicles were better developed. The intes- 

 tine contained a small amount of food material and was 

 nine or ten inches in length; most of this growth had 



