THE AXIAL GRADIENTS IN HYDROZOA. 



2OI 



primary basipetal gradient like attached quiescent animals 

 (Figs. 32-35). Cases of this sort have not been observed in H. 

 oligactis. 



Animals which have been attached only a short time, e. g., an 

 hour or two, preceding exposure to the reagent, and animals 

 which attach themselves in the solution, usually show gradients 

 like those of the detached animals, i. e., basipetal in tentacles 



55 



:^ 



n 



60 



"*-'!/ ' 



-. - 



lit - 



' 



'.-"" 



57 



58 



FIGS. 55-64. 



59 



and body and acropetal from the foot, or in both directions from 

 some level of the stalk. In these cases there is usually more or 

 less activity of the stalk for a time after attachment, and appar- 

 ently the condition of excitation persists for some time after 



