CELLULAR BASIS OF MORPHOGENESIS IX THE SEA URCHIN 507 



ditference can partly be reduced to a quantitative change of some basal 

 activities. It may furthermore be permitted to state that pseudopodal 

 elements play an important role in morphogenesis. Such elements are no 

 doubt excellent morphogenetic tools as they not only provide a force which 

 gives rise to translocations and deformations, they also find the suitable 

 direction for the forces by random exploration — and thereby contribute 

 to a proper integration of the organ rudiments to form an organism fit for 

 survi\al [2]. 



It is easv to make a long list of problems for future research. One of the 

 most important problems is how the time sequence for the release of the 

 processes concerned is determined, how the borders between the indi\"idual 

 organ rudiments is determined and why they are so sharp, and why the 

 future development of the cells in the different regions diverge. The only 

 point I will make in this connection is that I think that the control of the 

 time-sequence may be a strategic point where the analysis should start. A 

 properlv controlled time-sequence mav serve as a good basis for a feed-back 

 control of development of less ad\anced rudiments bv older ones. 



Finally, may I add a personal comment : I think that the gap between 

 the organ level and the molecular events can be bridged if we trv to under- 

 stand the biochemical basis for pseudopodal formation, pulsatory activity 

 and changes in adhesion between the cells and similar phenomena. 

 Willmer [S] has indicated one wav in which such relationships between 

 cellular morphology and the biochemical level can be studied. I refer to 

 his work with the amoeba Xotg/eria i^nihcri which he is able to transform 

 from an amoeboidic cell into a flagellate one, and vice versa, merely by a 

 change in its chemical milieu. And Runnstrom, cf. [7], has long ago 

 focused our attention on the metabolic gradients in the egg which no 

 doubt appear to be paralleled by gradients in morphological behaviour of 

 the cells. And therefore, as a final personal confession to the participants 

 in this symposium, where much is said about oxidati^■e phosphorylation: 

 the day may come when I, or at least mv grandchildren, begin to look 

 upon the discussion between "phosphorylatiAe fans" as something more 

 than a bullfight. 



References 



1. Gustafson, T., and Kinnandtr, H., Exp. Cell Res. II, 36 (1956). 



2. Gustafson, T., and Kinnander, H., E.xp. Cell Res. 21, 361 (1960). 



3. Gustafson, T., and Wolpert, L., Exp. Cell Res. 22, 437 (ig6i). 



4. Gustafson, T., and Wolpert, L., Exp. Cell Res. 22, 509 (1961). 



5. Gustafson, T., and Wolpert, L., Exp. Cell Res. (in press). 



6. Kinnander, H., and Gustafson, T., Exp. Cell Res. 19, 278 (i960). 



7. Runnstrom, J., I'erluuidl. Deittsch. Zool. Ges. in Tiibingen, p. 32 (1954). 



8. Willmer, ¥.. X., "Cytology antl Evolution"". Academic Press, Xew York, 

 London ( i960). 



