-54 



and on sand weighted (40g) of 15 g (See p. 21). The above study 

 of the mechanics of the deviation does not pretsnt to be statist!- 

 oally comprehensive. The objact is merely to point out that the 

 "deviation push" can be always increased bu weighting down the animal 

 and that in the sea urchin, which uses its spines, and in Pyonopodia 

 which does not attach tightly while pulling hard (Soe p. 22) the pull 

 oan also be increased by weighting down the animal. The relation* 

 ships of pull, and deviation push in the loaded and unloaded Asterijia 

 and i'isastar, are consistent with the above and comparable, quanti- 

 tatively to the pulling ability of the animals, both loaded and un- 

 loaded on sand* 



Thus, the attaching reflex that strangthens with the resis- 

 tance to the ordinary step (see p. 19) does not appear comparably 

 in the deviation reaction. This it seams to me is because the tube 

 feat on one side of the obstacle overbalance in their traction those 

 on the other side, cause a rotation of the animal in that direction 

 and the various tube feet coordinate in the direction of this rota* 

 tion. There is than no resistance to the step bi'.t merely a devia* 

 tion of it in one direction or the other brought about by its relation 

 to the substrata* 



Another fict pointing to the conclusion that the factor* 

 of the deviation reaction have to do with the mechanical relation* 

 ship of animal to substrate rather than with reflexes having their 

 receptors at the point of contact is that if the tips (Asterina) 

 of the rays instead of the dermi. between the rays com* in contact 

 Tith one obstacle connected with the spring recorder the amount of 

 pressure that it takes to cause a change in direction, does not 

 vary if weight is put on the back of trie starfish, Xhe value it 

 about 2.5 g in each case* This shows 



