JOURNAL OF ANIMAL BEHAVIOR 



Vol. 2 NOVEMBER-DECEMBER, 1912. No 6. 



LITERATURE FOR 1911 ON THE BEHAVIOR OF 

 LOWER INVERTEBRATES 



MARGARET FLOY WASHBURN 



Vassar College 



Protozoa. Two studies of geotropism in microorganisms ap- 

 peared during the year 191 1, both of them tending to support 

 the view that the effect of gravity is rather a mechanical one, 

 like its effects on lifeless bodies, than that of a stimulus to which 

 the organism responds through the irritability of its protoplasm. 

 Harper (13) placed Paramecium in a medium containing very 

 fine particles of iron. When too much iron was ingested by 

 the animals, they sank to the bottom, but when a moderate 

 amount had been taken, there was a tendency to move upward, 

 which Harper ascribes to the fact that the posterior part of the 

 body had had its weight increased by the iron. On the other 

 hand, when finely divided paraffin, a substance lighter than 

 water, was ingested, the opposite tendency was shown. Harper 

 cannot accept the theory of Lyon, that Paramecium orients 

 itself by active movements in response to the stimulus of parti- 

 cles within the body, as in a statocyst, for, he says, "It is not 

 easy to see how an animal revolving continually on its axis 

 could react to the localization of an internal stimulus." The 

 evidence which Lyon obtained for his hypothesis by centri- 

 fuging the animals, namely, that under such circumstances the 

 anterior end is directed outward and is therefore probably 

 heavier, so that normal negative geotropism, with the anterior 

 end up, must be active, Harper would set aside by explaining 

 the position of the anterior end as due to the animal's compen- 

 satory movement against the rotation. Massart's observations 

 that the positions assumed by dead infusoria are not identical 

 with those assumed in reactions to gravity, as should be the 



