REGENERATION IN THE HYDROMEDUSA, 
GONIONEMUS VERTENS. 
T. H. MORGAN. 
HAECKEL,! in 1870, stated that he found the power of regen- 
eration remarkably developed in several species of medusz be- 
longing to the family Thaumantide. He discovered that if a 
medusa be cut up into more than a hundred pieces, each. piece, 
provided it contains a part of the margin of the bell, will develop 
a complete medusa (“eine vollständige kleine Medusa”). The 
little medusa developed in a few (two to four) days. Even a 
single tentacle, if it contained at its base a small part of the 
margin of the bell, would make a new medusa. No details are 
given, and it is not possible to gather from the account whether 
new organs developed, as one would expect, if the little medusa 
was complete (vollständig), or whether only the medusa-form was 
assumed by the pieces. 
Haeckel also added that if the segmented egg, or even the 
ciliated larva, was cut up into many pieces, each piece would 
make a new small larva. 
Hargitt? described in 1897 the results of a number of experi- 
ments that he had made on the regeneration of the medusa 
Gonionemus. He found that excised portions of the margin of 
the bell regenerated promptly, but it is not clear in this case 
whether he meant by regeneration that the cut edges closed 
together, or whether the parts cut off were replaced. When 
the medusa was cut into two equal pieces, each became an 
“independent and perfect medusa.” The restoration was some- 
what peculiar. “It would seem to be a recovery of form and 
function rather than regeneration in the usual sense of that 
term.” ‘The new meduse were in most respects quite simi- 
1 Monographie der Moneren., Biologische Studien, Heft 1 (1870), p. 23. 
2 Hargitt, C. W. Recent Experiments on Regeneration, Zodlogical Bulletin, 
1897, vol. i. 
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