THE AXIAL GRADIENTS IN II Yl>R< >Z< > A . 193 



apolar form- with a few normal blastuke; after four day- chiefly 

 .tpnlar forms with a few inhibited planuKi-: solution now 

 diluted one third; after nine days chiefly outgrowing -n axes 

 and apolar form- with a few stolon axes giving ri-e \<> hydranths; 

 after t\\el\e day- chiefly new hydranth-stem :'i-mg directly 



from previou-ly apolar forms and hydranth-stem axes ''-ing 

 fn>m -tolon a\e-, with a few stolon axes bearing no hydranth- and 

 a fe\\ .1] i ilar form- still remaining. 



M 'Mil i< VTION OF DEVELOPMENT IN Gonothyr 



\ fe . riments with HC1 and KCN. e\po-ure beuinnin;; 



\\ith tin- early planula after emergence from the i;onophore. v 

 -niii- ii-nt t' -how that the modifications result in v, tM-m dit- 



nt ial inhibit ion and from differential aivliinat i< m ami rr - >\ i r\ 

 an- i IK- -aiuc in Gonoihyrcea as in Phialidium. To <!< in pi 1 



tin- -MM rptiliility of Gonothyrcra is less than that <>t I'hiulidinni. 

 I"! cxaiMjilc. IK'I, |)Ii 7.4 has very little inhibiting rlk-ct mi 



"tliyrad. tlu- planula- usually attaching in the normal mamu-r 

 and i:i\ ing rise to hydranth-stem axes without stolon out^n>\\ ths. 

 S ties 3 I. of Table I. shows that this pH is stronjv inhibiioiA 

 1"i /';i(ili<Hnw. l-'or obliteration of j)olarity in Gonothynca a 

 concentration of HCI giving pH 7-6.8 was found to In- iu-cr--ar\- 

 and .1- ai cliniai ion occurred, stolon axes developed and ( \ < -n . 



to hydranths. As might be expected from these result- 

 . 1 1. \\dinv; \\ iili the medusa 1 had little or no effect on di-\ rlopmnn 

 \\ithin i In- rair s i- used for Phialidinm. 



DlSCfSSION. 



Tlu dilU-rentially inhibiting effect of the agent- on tin- bla-tula 

 and -arl> ])laiuila stages is sufficiently evident. In tin- normal 

 bla-tnla tin- region of basal thickening and of immigration 

 iipn-tnt- the low end of the apico-basal gradient (Child. '25 

 and the effect of the agents is to bring higher levels of th< rut 



into a condition in which they behave like- tin- ba.-al n-^ion. In 

 tlu- cAtivmc ca-L-s (Figs. IO-I2) in which polarity i- apparently 

 obliterated, the whole blastula wall, includin- e\ en the ajiical 

 pole. beha\e- like the basal region. Taking this behavior 

 critenon, it a|i|n-ar- to be true that the whole bla-tula i- redu< ed 

 i<> the |)h\ -iolo-it al level of the basal region. Kvidently -IK h a 

 13 



