304 MORGAN. [VOL. II. 



rings of wire between which, at equidistant points, were 

 sixteen paddles (5 cm. x 8 cm.) made of oblong pieces of 

 sheet-copper; spokes (13 cm. long) attached the rings to an 

 axis that rotated in two sockets. When the wheel was immersed 

 in the water of an aquarium, and a stream of water from the 

 tap was made to play (beneath the water) on the plates, the 

 wheel slowly revolved, making about five and one-half revo- 

 lutions in a minute. 1 



Pieces of Antennularia were attached to the wheel in the 

 following way. Sheets of cork of the same size as the copper 

 plates were attached to the underside of the latter by wire or 

 string. Pieces of the hydroid were fixed to the cork in different 

 positions by means of crossed cactus spines. The pieces were, 

 on an average, about 15 cm. from the axis of rotation. The 

 results were entirely negative. None of the pieces produced 

 either roots or stems ; and the pieces died sooner than did those 

 in other experiments. As this experiment was carried out in 

 a different aquarium, I cannot be certain that the death of the 

 pieces was not due to other causes than to the rotation. 

 Furthermore, it is not evident from the experiment whether 

 the rubbing of the moving ends against the water suppressed 

 the regeneration, or whether the result is due to the continuous 

 change of position in regard to gravity. The rotation was too 

 slow for the action of the centrifugal force to have played any 

 important part. Since other experiments have shown that roots 

 may develop at both ends of a piece suspended vertically, it 

 is improbable that in the rotating pieces the changing posi- 

 tion in regard to the action of gravity can account for the 

 result, and it is much more probable that the motion of the 

 piece through the water interfered with the regeneration at 

 the ends. The experiment needs to be repeated more often, and 

 other check experiments carried out in the same tank. 



The work that I have done on the regeneration of Antennu- 

 laria, while incomplete in many ways, shows at least that other 

 factors than gravity enter into the result. I do not question the 

 main part of Loeb's results, for they seem to show that gravity 



1 This wheel was left at the Naples Station in the hope that it might be used 

 by some one to continue the experiments. 



