THE AXIAL GRADIENTS IN HYDROZOA. 9! 



more apical branches are negative to the apical regions of the 

 more basal branches. 



The Gradient of the Medusa Bud. In the naked medusa buds 

 of Bougainvillea and other tubularians the gradients in rate and 

 amount of reduction of KMnO 4 appear very distinctly. 

 The free apical end of the bud always shows the high- 

 est rate and greatest amount of reduction, as indi- 

 cated in Fig. 5, a young bud of Bougainvillea. The 

 medusa buds of the campanularians constitute less 

 favorable material because the crowding along the 

 blastostyle and the presence of the gonotheca render 

 it impossible to insure uniform concentration of per- 

 manganate over all parts of the surface. In general, 5 

 however, it is perfectly clear that the apical regions of 

 these buds reduce permanganate more rapidly and in greater 

 amount than other levels. 



In Gonothyrcea the rudimentary medusae or gonophores in the 

 later stages of development come to lie outside the gonotheca, 

 though still attached to the blastostyle, and so are directly 

 exposed to permanganate solutions. The rate of reduction is 

 highest in the small tentacles of these gonophores and decreases 

 basipetally over the outer surface of the body. The subumbrellar 

 cavity of the gonophore is at first closed and never widely open 

 to the exterior, so that it is not possible to determine with 

 certainty the relative rate of reduction in this region, though it 

 is probably much the same as in other medusae. In the old 

 gonophores after extrusion of the planulae the reduction gradient 

 may be almost or entirely absent. 



REDUCTION GRADIENTS IN FREE-LIVING HYDROMEDUSJ. 



The simple experiment of placing medusae in a permanganate 

 solution and agitating sufficiently to provide for uniform distribu- 

 tion of the permanganate was performed repeatedly during three 

 summers and always with essentially the same result. In all 

 forms examined reduction occurs most rapidly in the marginal 

 tentacles and the oral lobes or tentacles, when such are present. 

 Each tentacle or lobe shows a gradient in rate of reduction, 



