THE AMERICAN NATURALIST [Vol. XLI 



complete somersault by means of the tentacles. At first this was 

 observed in medusae resting in the sunlight; the action was like- 

 wise seen in animals in the shade so that it has nothing whatsoever 

 to do with the effect of light. 



In the notes previously published, the writer made an attempt 

 to determine the cause of the peculiar behavior of the animal in 

 inverting the bell on reaching the surface of the water. The 

 medusa has no mechanism other than contact whereby it can 

 turn the bell on a transverse axis and thus invert it; it is never 

 observed to turn in its path abruptly. As the equilibrium of the 

 bell is destroyed when the animal reaches the surface and pushes 

 one edge of the bell through the surface film, the inversion occurs. 

 It frequently happens that medusae are found that will not remain 

 mouth down even when so placed by hand. Such individuals kept 

 from inverting })ulsate violently for long intervals and come to 

 rest only when they are turned over. 



In the paper just cited, the writer interpreted the accumulation 

 of Gonionemus in the shade as the result of trial and error. Further 

 work has strengthened this conclusion. Only in the s])e('ial case 



