44 HARGITT. [VOL. I. 



following morning in a partially disintegrated condition, a 

 result due in part to the unusual temperature, and perhaps in 

 part to overfeeding. 



A series of experiments were undertaken by which to secure, 

 if possible, by artificial means other inversions of a similar sort, 

 and though various expedients were adopted by which to facili- 

 tate such, they gave no permanent results. 



The phenomenon of eversion in the Medusae of Obelia and 

 other Hydroids in their young or newly discharged condition 

 is quite well known, but it continues for a brief time only, and 

 with no disposition toward permanence so far as I have known. 



Of course the classical experiments of Trembley (1744), 

 Nussbaum ('87, etc.), and others upon Hydra are too well 

 known for special comment, and at first sight might be 

 thought to be analogous to that now under consideration ; but 

 a moment's reflection will suffice to show that it is only so in 

 a very general way. For example, there is no inversion of the 

 relative position of ectoderm and endoderm, since the lining 

 of the bell, outer surface of the manubrium, etc., is ectodermal. 

 The enclosed cavity of the everted specimen served no new 

 function in its changed condition, nor did the outer layer in 

 its new relations. That any change in the histological charac- 

 ters would be induced may therefore be considered very un- 

 likely since the change of relative position, while considerable, 

 is yet not such as would necessitate any change of function. 

 Nevertheless the fact is an interesting one, and apparently 

 quite unique. At one time, just about the completion of 

 union of the inverted margins, a decided papilla-like bud ap- 

 peared at the aboral area which presented some resemblance 

 to a second manubrium, but this soon after was absorbed 

 entirely, and was probably only the elevation due to the 

 approximation of the margins preparatory to final union. 



V. Regeneration and HetcromorpJwsis. 



In connection with the foregoing experiments occasion was 

 taken to repeat some of my earlier experiments on regenera- 

 tion and to extend them somewhat. At an earlier point in 



