THIGMOTAXIS OR STEREOTROPISM 35 



pseudopod. Such a reaction is of evident service to the 

 Amreba in leading it into contact with objects where it 

 secures food and protection. The process of food taking 

 itself is probably dependent to a certain extent upon a 

 thigmotactic motion. Strong contact such as striking a 

 pseudopod with a needle causes the reverse or withdrawing 

 reaction. By repeated application of the stimulus to one 

 side Amoeba may be driven about in any desired direction. 



Paramoecia were found by Jennings to react to contact 

 by collecting against solid objects. Often bits of substance 

 are fairly coated by these infusorians. The cilia in contact 

 with the object cease beating and stand out at right angles 

 to the body while the cilia of the oral groove and sometimes 

 also in other parts of the body, continue their movement. 

 Among the hypotrichous infusoria the tendency to keep in 

 contact with solids is very strong. In these forms the cilia 

 on the under side of the body are metamorphosed into cirri 

 which are employed hi running about over objects much in 

 the same way as an insect uses its legs. An Oxytricha is 

 described by Verworn as happening to get upon the round 

 egg of the clam Anodonta. It ran about for hours unable 

 to leave the surface since the egg rested on the bottom at 

 only one point. 



The infusorian Loxophyllum is usually engaged in gliding 

 about on its right side. It is apparently indifferent as 

 regards orientation to gravity, as it will move about on the 

 under side of a surface film with its right side uppermost 

 as well as on the bottom. When turned over on its left 

 side it rights itself in several different ways. Even small 

 pieces show the same tendency to keep the right side in 

 contact with solids and they will also right themselves 

 when turned over. Much of the righting movements of the 

 lower animals consists in the effort to keep a certain side hi 



