REGENERATIVE POTENCIES OF DISSOCIATED CELLS. 375 



such morulae as those of Pennaria or Turritopsis or Hydractinia 

 it would include practically the entire range of shape exhibited 

 by these regeneration aggregates, and one might designate them 

 as regeneration morulse, for such they really seem to be. 



Encystment. — Following the process of aggregation there oc- 

 curred in those vitally active a process of encystment, that is, 

 the secretion of a definite perisarc about the entire mass, and 

 its adhesion to the bottom of the glasses. Lest this feature be 

 regarded as peculiar to these particular cases it should be pointed 

 out that the phenomenon is often shown at a certain stage in the 

 normal development of the hydromedusae, and indeed in some 

 scyphomedusae as well. The writer has directed attention to 

 this in the case of Cyanea ('02, '10) and it is doubtless shared by 

 many others. Its function is doubtless protective, just as is 

 that of the perisarc in the adult hydroid. Encystment usually 

 occurs shortly following the completion of the phase of aggrega- 

 tion just described. This encysted stage may continue for an 

 indefinite time, or it may be of short duration. The latter was 

 more frequently the case with Podocoryne than with some others. 

 In the present case the cyst was frequently ruptured for the up- 

 growth of the hydranth within a comparatively short time, say 

 two days; but in many cases this stage persisted for a week or 

 even more, and indeed in certain cases the cyst became a prison, 

 being so dense as to become impenetrable from within as well as 

 without. This again is comparable with what may happen in 

 such stages in normal development (vide supra). This process 

 of perisarc formation often takes various forms, following the 

 phases of growth. In Podocoryne there was frequently the 

 development of a reticulated hydrorhiza before the appearance 

 of a hydranth, and later there appeared nodular enlargements of 

 these stolon-like tubes and from these points would occur the 

 upgrowth of a series of polyps. In one such preparation I 

 obtained three vigorous young hydranths. 



What has been stated in this connection as to Podocoryne is 

 likewise true of other species experimented with. The behavior 

 of the encysted aggregation morulae is quite like that of the grow- 

 ing stolons of the hydrorhiza. Both may live for weeks under 

 these conditions without any signs of further development. 



