322 G. H. PARKER 



some internal mechanism such as small heavy particles con- 

 tained within its substance. 



The means by which the geotropic response is accomplished 

 is in no sense clear. Torrey ('02, p. 39; '04 a, p. 403; '05, p. 

 334; '10 b) in a series of experiments was led to favor the view 

 that the response was the result of tension or growth changes in 

 the vacuolated axial entoderm and not due to neuromuscular 

 activitjr, thus bringing the reaction in line with the methods 

 known to obtain in plants rather than in animals. This view 

 was supported by the slowness of the reaction, a feature 

 common in the geotropism of plants, and by the fact that if 

 numerous tranvserse cuts are made in the stalk of Corymorpha 

 so as to interrupt the longitudinal muscle but leave the axial 

 cells essentially intact, the response is still carried out though 

 imperfectly. 



I have confirmed Torrey's observation that a stalk of Cory- 

 mopha cut as he described will still exhibit negative geotro- 

 pism, but I have also shown that transverse transmission occurs 

 in the Corymorpha stalk and that, therefore, neuromuscular 

 activity may spread around cuts such as Torrey made; it is, 

 therefore, still possible that this response may depend upon the 

 muscles rather than the contained parenchymatous cells. To 

 test this question I employed other methods than those used by 

 Torrey. 



The parenchymatous core cells in Corymorpha can be very 

 generally destroyed by passing a rough needle down the axis 

 of a stalk and then gently twirling it round and round. As a 

 result of this treatment the stalk is left as a rather limp tube 

 but one which nevertheless in seawater has some resistance. 

 Six such stalks with their axial cells bored out were mounted in 

 horizontal positions and their responses watched. Five of these 

 eventually turned up into approximately vertical positions in 

 times that ranged from two hours to four hours and a half. 

 One never moved much out of the horizontal. An examination 

 under the microscope of the interior of those that responded 

 showed that their axes were filled with a pulp of vacuolated 

 cells and cell fragments that made it clear that these cells played 



