Regeneration in Hydromedusae 5 



placed. Pieces of equal length grafted by oblique surfaces de- 

 veloped anlagen squarely placed. While I gave no particular 

 attention to this feature, nor investigated the conditions active 

 in bringing about this phenomenon, in general it was noted that 

 both long and short pieces which had been cut obliquely had the 

 anlagen squarely placed. 



The results of some of the principal experiments are sum- 

 marized below. 



Experiment 5. — Twenty pieces of Pennaria were placed in 

 a dish, the bottom of which was covered with sand, in the fol- 

 lowing- way: The pieces were stuck into the sand so that the 

 main stem was vertical. The branches did not touch the sand, but 

 were entirely surrounded by water. Some pieces were fixed with 

 the distal end in the sand, others with the proximal. Several 

 pieces of stolons were also fixed upright in the same manner. 

 Regeneration was very slow, though it was never as rapid in this 

 species as in Tubnlaria or Endendrium. After several days con- 

 siderable new growth had taken place and new perisarc secreted 

 around this growth, but then the coenosarc had withdrawal , 

 leaving the perisarc empty. This growth occurred on all the 

 pieces and was quite irregular, extending in all directions. 

 After this had continued for several days, hydranths began to 

 develop. The first one appeared on the proximal end of a stem 

 (distal end in the hand), though very soon another one formed 

 on the distal end of the stem (proximal end in the sand). Hy- 

 dranths continued to develop for a considerable time, seeming to 

 form as readily and at about the same rate from the proximal as 

 from the distal ends. A hydranth also formed from the upper 

 end of one of the stolons (^fig. 7). In several specimens hy- 

 dranths formed on the distal ends of branches which pointed 

 <lownward and later turned directly upward (fig. 6). The first 

 indication of a developing hydranth is the formation of a knob 

 by the coenosarc. A thin perisarc is secreted around this, and 

 the knob may increase in size a little or become elongated. The 

 ])erisarc is ruptured, the knob of coenosarc pushes out and forms 

 a hydranth, the tentacles first appearing as small buds or out- 

 growths and reaching mature size by new growth. In one speci- 



279 



