REGENERATIVE POTENCIES OF DISSOCIATED CELLS. 379 



state, at the time it is subjected to the test. This has been 

 recognized in principle in experiments on ordinary regenerative 

 processes, in that only especially vigorous specimens are used. 

 Further discussion of this point will be deferred to another section 

 of the paper. 



Other Species. — As indicated in the outstart, about a dozen 

 difTerent species were tried in the course of the investigation. 

 Among these were several campanularian hydroids and two 

 species of medusae. The hydroids tested gave the same initial 

 responses as those just described for Tubularia, but beyond 

 that the results were likewise negative. In all cases the phase 

 of cell-aggregation was essentially the same as in the former cases. 

 The same was likewise true of the internal organization of the 

 morula-like embryo, and in the perisarc formation, but beyond 

 this there was no development. 



Species of sertularian hydroids and also of Halecium were 

 tested and gave exactly the same initial responses, including 

 encystment of the embryonic mass which lived for a time but 

 soon showed signs of disintegration and death. The reactions 

 of the last species were the least satisfactory of any tested. 



Medusce. — Two species of medusae were tried, though with 

 hardly any hope of getting any regenerative responses. They 

 were prepared just as had been the hydroids, strained through 

 the bolting cloth and set aside after addition of fresh water. 

 An examination of the dissociated cells showed about the same 

 condition of the other preparations, and further inspection in 

 about an hour showed a series of the most beautiful cell-aggre- 

 gates found in any of the experiments. When it is recalled that 

 Medusae represent the most highly specialized group of Hydrozoa 

 it will seem strange to find cells thus organized after having been 

 dissociated in the manner indicated. In all my observations 

 upon coelenterate development I have seldom seen more typical 

 blastula-like embryos than those under review. Unless one were 

 actually aware of their source he could hardly have been con- 

 vinced that they were not genuine embryos in process of develop- 

 ment. However, so far as my experiments show the regenerative 

 process does not go farther. Moreover, the organism thus formed 

 is very short lived, and devoid of further significance so far as our 

 problem is concerned. 



