414 THE SPECIAL SENSES. 



Some interesting results reported] by Streeter,* from experiments 

 made upon tadpoles, demonstrate in a striking way the impor- 

 tance of the labyrinth to the power or property of equilibration. 

 Up to the sixth day after fertilization the tadpole shows no evi- 

 dence of a power of equilibrium, and is not capable of swimming 

 freely in the water. When the auditory vesicles appear, after the 

 sixth day, the animal exhibits evidence of a sense of equilibrium 

 and swims freely in the water out of contact with solid substances. 

 If at or before the beginning of this stage one of the auditory 

 vesicles is removed, the tadpole shows evident, although tem- 

 porary, signs of a defective power of equilibration. If both 

 vesicles are removed the animal seems to lose permanently its 

 power of swimming, and when at rest lies in any position, as though 

 it were lacking in a sense of equilibrium. 



* Streeter, "Journal of Exp. Zoology," 3, 543, 1906; also vols. 4 and 16. 



