REGENERATIVE POTENCIES OF DISSOCIATED CELLS. 383 



it emerges from the tube. They are waste material rather than 

 formative substance" ('oi, p. 414). The writer himself has 

 made similar observations in several cases, and has demonstrated 

 the regressive condition in the coenosarc of hibernating specimens. 



A most interesting study of a series of changes of apparenly- 

 similar character has been made by Schultz, "Uber Hungerer- 

 scheinungen bei Hydra fusca" ('06), discussed under the larger 

 topic of "Reductionen," under which are considered a series of 

 marked phenomena observed in organisms of various grades of 

 complexity, including Planaria, Lumbricus, Molosoma, etc. 



Similar experiments by Greeley ('03), on "Effects of Variations 

 of Temperature on Animal Tissues," show essentially the same 

 phenomena. Among these experiments some made on Hydra 

 are especially pertinent in this connection. To quote, "It was 

 at once observed that whenever a Hydra is exposed to a tempera- 

 ture of 4° to 6° C. the tentacles gradually become thicker and 

 shorter, and finally are completely absorbed into the body. As 

 the absorption goes on, the ectoderm and entoderm cells of the 

 tentacles lose their individuality and form an undifferentiated 

 mass of protoplasm, which is slowly resolved into the body of the 

 Hydra. The tentacleless body of the Hydra becomes slowly 

 resolved into a dense spherical mass of coagulated protoplasm, 

 in which no distinction between individual cells can be made out, 

 and remains in this condition as long as it is kept at a low tem- 

 perature, but quickly forms tentacles and a double layer of cells 

 again when it is returned to the temperature of the room" (p. 43). 



Enough has now been said to show, I think, that only in some 

 qualified sense can one use such terms as irregular, meaningless, 

 abnormal, pathological, etc., in describing phenomena such as 

 those involved in the experiments and results under review. 



As a final note it may be stated that in my experiments no 

 attempt was made to detach and isolate the several cell-aggre- 

 gates such as was done by Wilson. Neither did I attempt to 

 augment the masses by artificially bringing several masses into 

 contact as he had done. Attention has already been directed 

 to the fact that there was some evidence that from larger masses 

 were derived larger polyps, and that below a certain minimum 

 size there was no evidence of growth. 



