LIBBIE H. HYMAN. 



cells. But this is not the only retarding factor in such pieces. 

 The coenosarc after the death of the apical end withdraws into 

 the perisarc leaving a short apical region of empty perisarc- 

 This empty perisarc crumples to a greater or less extent. There- 

 fore when the hydranth does regenerate it has to push out 

 through this empty region before it can unfold, and this of itself 

 would further delay the time of emergence of the oral hydranth; 

 but to make matters worse, the crumpling of the empty perisarc 

 renders it very difficult for the hydranth to push its way to the 

 surface. On account of all of these factors, the regeneration of 

 the apical pieces is very greatly delayed when they are cut in 

 the manner employed by Banus. In fact, in many cases, the 

 oral hydranth is so greatly retarded that the aboral hydranth 

 emerges first, and in a few cases, the oral hydranth never emerged 

 on such pieces, a complete reversal of polarity with disappearance 

 of the primordium of the oral hydranth having been observed. 

 Presumably Banus failed to notice whether oral or aboral hy- 

 dranths had emerged, but the two ends of such pieces are easily 

 distinguished by the bit of empty perisarc so that there is no 

 doubt of the correctness of my statements. Not only are the 

 oral hydranths of these pieces delayed but they are often ab- 

 normal in appearance; they are enlarged and distended, owing 

 probably to the pressure to which they are subjected in being 

 forced out through the crumpled perisarc, and their tentacles are 

 short and stumpy. They regulate to normal within a few hours 

 after they have emerged. In two or three cases, partially 

 doubled hydranths were produced. 



The three experiments performed with pieces cut in the way 

 employed by Banus and as represented in Fig. 5 are presented in 

 Table XI. They were performed in December and regenerated 

 at a temperature of 12 C. 2. Experiment 31 consisted of 

 pieces 5-8 mm. long, the other experiments of pieces 10-12 mm. 

 long. In connection with experiments 39 and 49, the number 

 of both oral and aboral hydranths emerged on the apical pieces 

 at each observation is given. These records include of course 

 only those cases in which the aboral hydranths emerged first. 

 In some of these cases the oral hydranths subsequently emerged, 

 and this is indicated by the number in parenthesis which follows 



