No. i.] RECENT EXPERIMENTS ON REGENERATION. 



o o 



the aquarium, and many perished before regeneration of these 

 organs had gone forward to any considerable extent. Of its 

 reality, however, there is not the least doubt. The rate of re- 

 generation in these cases was much slower than in the former, 

 as would be naturally expected, in most cases requiring a fort- 

 night to afford conclusive indications of the new organs. 



Most marked in many respects is the condition indicated in 

 B of Fig. 5, the resultant of B, Fig. 4. That is, the excised 

 margin had become a new medusa. But in this case, as in the 

 vertical sections, the process appeared as more a restoration of 

 form through a marked and continued contraction of the mar- 

 ginal walls, and a final union of their upper margins to form 

 the dome of the new medusa. Again there seems to have 

 been no evidence of growth in substance, which would in this 

 case have been impossible, since the absence of mouth Di- 

 gastric cavity would render the taking of food entirely out of 

 question, and there would also be a draft upon any reserve 

 energy in the tissues in the mere maintenance of life and the 

 usual waste incident to existence. And this fact of itself 

 makes the results more interesting ; namely, that in a minute 

 fragment of the nature of the one under consideration there 

 seems to be an intrinsic potency to recast itself into the 

 morphological equivalent of the original ; and that this dis- 

 position was manifest in even the minutest portion from 

 any part of the body. So marked, indeed, was this ten- 

 dency that it almost seemed as if there were present some 

 occult organic crystallization prepotency, if such a phrase or 

 comparison be tolerable. 



Such in brief is an outline of the facts concerned in the 

 experiments. Their significance in relation to others of like 

 character and to problems of current biological importance 

 will be more or less apparent without special emphasis. It 

 may not be amiss, however, to refer briefly to some theoretical 

 considerations upon which they would seem to have special 

 bearing. 



Concerning the problem of the more primitive character of 

 hydroid or medusa no additional light is afforded. If the more 

 highly developed and specialized nature of the medusa is 



