REGENERATIVE POTENCIES OF DISSOCIATED CELLS. 373 



of the entire series. Several colonies were brought in, all occupy- 

 ing shells inhabited by hermit crabs, the usual habitat of this 

 species. In one respect the species is rather difificult to operate 

 on owing to the spinous condition of the basal coenosarc, which 

 made it hard to obtain enough of the polyps to make the desired 

 culture. By allowing the colony to expand fully in shallow 

 dishes it was possible by a dextrous sweep of the scissors to cut 

 off quite a bunch at a single time, and by allowing others to 

 expand in the same way and repeat the operation it was found 

 possible to secure sufficient material for the culture. The speci- 

 mens were finely cut or ground into a pulpy mass, filtered through 

 the sterilized cloth, and thus fitted to undergo later changes. 

 It may as well be stated here that among hundreds of prepara- 

 tions relatively few gave completely successful results in the 

 regeneration of new polyps. My first surprise was not that many 

 of the preparations "went bad," but that any survived the opera- 

 tion and went forward in regeneration. Here as in most experi- 

 ments on regeneration a large mortality occurs in the prepara- 

 tions. 



Character of the Dissociated Cells. — If examined soon after 

 their dissociation one may easily distinguish the several sorts of 

 cells even under a magnification of three hundred diameters, 

 that is, ectoderm, entoderm, nematocyst, interstitial, etc. The 

 very minute ectoderm cells are in striking contrast with the 

 large flagellated cells of the entoderm. In the course of an hour, 

 sometimes less, these differences become less marked, and ulti- 

 mately almost disappear. They have become despecialized into 

 potentially embryonic cells, and probably from this change have 

 acquired their regenerative capacities. A careful study of such 

 dissociated cells from various species has strongly suggested the 

 probability that some such cytomorphic process is involved in 

 most regenerative phenomena, and leaves little doubt that the 

 features under consideration here are positively brought about 

 through such a process. 



Cell Aggregation. — Examination of a culture within a few 

 hours, three to five, will show that a remarkable change has 

 taken place among the cells in their relations to each other. Thej^ 

 will be found to have formed numerous small nodular groups 



