404 



THE AMERICAN NATURALIST [Vol. XL 



however, they bend outward and the manubrium turns them to- 

 ward the stimulated side. If they then touch the meat, they close 

 up around the moutii. 



These reactions make it ap])ear as tliough the procuring of food 

 depended wholly uj)on mechanical stinuilation, as Torrey has 

 claimed in the case of (\)rymorpha; but the following experiments 

 have led to a somewhat dill'erent conclusion. Wlien a grain of 



upon the proximal tentacles and lo touch thnh'stal ono. Miid a 

 piece of meat is placed in a corresj)on(hiii;' po-ition on the opposite 

 side, the numubrium almost invariablv tiini> toward the meat and 



froin the mouth of a pii>ette on the pfoxinia! icutach's, no reaction 



pand and the manubrium bends tow ard the stiimihitcd side. To 

 prove that these reactions are not dtic to incchanical stinuilation 

 produced by particles of sohd matter or by currents, the same ex- 

 periment was tried using [x.wdered ( ai iiiiiie in sea water instead of 



turned toward the stimuhited side 



the turning and opening-out rau 

 trials (717). 



A third experiment points in th 

 tentacles of an active hydranth ai 

 needle, they close tightly over tl 

 they are touched again with the 



same manner with a piece of m<^•lt 

 open out and wave about. 



proximal tentacles are not. 



The effect of other chemical substances was tested w itho 



