THE AXIAL GRADIENTS IX HVDROZOA. 



The evidence from the course of development itself, from dif- 

 ferential cytolysis, from differential rate and amount of reduction 

 of KMnO 4 , from differential staining by neutral red and methy- 

 lene blue and differential reduction of the latter, agrees in indica- 







FIGS. 6-8. 



tin-. tir>t tin.' rxistence of a physiological gradient along the polar 

 axis from tin- oocyte to the planula stage with its high end at the 

 apical fiul i'f egg and larva, and second, the appearance in the late 

 pkuuila of a -tv.'iid gradient at the basal end, opposite in direction 

 to the first, and associated with the development of stem and 

 hydranth from this end. Figs. 10 to 17, illustrating diagrammati- 

 cally the polar gradients of various stages, are in part early stages 

 of tin- ri-ihu-tioii gradients with KMnO 4 < Fi^- io-1-M. in part 



