6l_0 Child, Driesch's harmonic equipotential systems in form-regulation. 



due to the fact that primordia of different sizes arise in a perisarc- 

 tube of approximately the same diameter, for the changes in the 

 distal tentacle-area (area II) are nearly double those in the proximal 

 tentacle-area (area IV), as is shown in my table (Child, 1907b, 

 p. 427, Table XIII). Driesch states (1908, p. 413) that I find 

 that „die Proportionalität in den positiven Anlageteilen des neuen 

 Hydranten sehr strikte bewahrt ist und dass nur die Zwischen- 

 stücke in ihrer Länge gegen sie verstoßen." I thake the „positiven 

 Anlageteile" to be the tentacle-areas (incidentally why should they 

 be called „positive"?). But I have shown that the changes in the 

 distal tentacle-area are in most cases nearly twice as great as those 

 in the proximal tentacle-area. 



Can we speak of approximate proportionality when such diffe- 

 rences appear as those which T have shown to exist? I believe we must 

 conclude that the proportions of the parts of the hydranth-primordium 

 are typically different according to the position of the primordia 

 in the stem, i. e., their distance from the oral end, and also accor- 

 ding to their polar position. In short the localization of the parts 

 of the primordium is not exen approximately constant in relation 

 to the length of the primordium. Tubularia then does not agree 

 with the characteristics of Driesch's harmonic equipotential systems 

 which have been quoted above. 



And finally, in the last of my papers on Tubularia, I showed 

 that it is possible to control experimentally to some extent the 

 proportions of the hydranth-primordium in Tubularia, or in other 

 words to determine the formation of primordia of typical different 

 proportions by different experimental conditions (Child, 1907 g, 

 pp. 317^ — 322). These experiments are briefly as follows: the four 

 areas of primordia developing from the oral end of the stems after 

 removal of fully developed hydranths were measured and compared 

 with those of primordia developing from the oral ends of stems 

 after the removal of primordia. Primordia developing after the 

 removal of primordia are somewhat shorter than those developing 

 after the removal of fully developed hydranths (Child, 1907g, 

 p. 318, Table I), but comparison of their proportions shows most 

 clearly that the distal portions, especially area I (Child, 1907 g, 

 p. 319, Table II), are relatively considerably longer, and the proxi- 

 mal regions, especially area IV, are relatively considerably shorter 

 in primordia following primordia than in those following ftdly deve- 

 loped hydranths. Evidently the development of a hydranth induces 

 changes in the stem proximal to it. When we remove developing 

 primordia, as in my experiments, these changes have affected the 

 distal part of the region where the new primordium will form, 

 more than the proximal, but by the time the hydranth has attained 

 full development the changes in the stem proximal to it extend at 



