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



alle maschinellen Einrichtungen, welche zu letzteren notwendig 

 sind, müssen bereits im Ei gegeben sein" (Herbst, 1901, p. 117), 

 rests on a similar basis. Moreover, it is not necessary to conclude 

 that the egg cannot be simpler than the adult organism because 

 we cannot at present prove that it is simpler. And when we take 

 into account all the facts, i. e., the conditions of development as 

 well as the constitution of the egg, the assumption that the egg 

 is simpler than the organism attains a higher degree of probability 

 than any other. 



We are then, I believe, justified in concluding that, so far as 

 it concerns form regulation, Driesch's „Autonomielehre" with its 

 „proofs" is simply a hypothesis, and a hypothesis which at present 

 has no solid basis in facts. A few of its characteristic features 

 may be summed up as follows: it proceeds at various points as if 

 the present status of our knowledge of the physiology of organic 

 form were final; it assumes the exclusion of factors which cannot 

 actually be excluded in any experiment; it seems to assume that 

 the capacity for future or prospective likeness in the parts or 

 elements is equivalent to present likeness, so far as morphogenesis 

 is concerned; it practically ignores „atypical" results of experiment ; 

 in certain cases, e. g., as regards Tubularia, it assumes that visible 

 localized differences are the only localized differences existing; it 

 interprets actual inequipotentiality in certain cases as „masked' 

 equipotentiality ; and finally different statements concerning certain 

 points, e. g., proportionality in harmonic equipotential systems, 

 are not consistent. 



We are indebted to Driesch for many facts and analytical 

 concepts of great value, but not as yet for a proof of „Lebens- 

 autonomie" in form regulation. 



Hull Zoological Leaborotory. University of Chicago. June 1908. 



Bi])liograpliy. 



Barcleen, C. R., 1902. Embryonic and Regenerative Development in Planarians. 



Biol. Bull. Vol. Ill, Nr."6, 1902. 

 Child, CM., 1904 a. Studies on Regulation. V. The Relation between the Central 



Nervous System and Regeneration in Leptoplaua: Posterior Regeneration. 



Journ. Exp. Zool. Vol. I, Nr. 3, 1904. 



— 1904 b. Studies on Regulation. VI. The Relation between the Central Ner- 

 vous System and Regulation in Leptoplana: Anterior and Lateral Regene- 

 ration. Journ. Exp. Zool. Vol. I, Nr. 4, 1904. 



— 1905. Form-Regulation in Cerianthus. IX. Regulation, Form, and Proportion. 

 Biol. Bull. Vol. VIII, Nr. 5, 1905. 



— 1907 a. An Analysis of Form-Regulation in Tubularia. I. Stolon-Formation 

 and Polarity. Arch. f. Entw.-Mech. Bd. XIII, H. 3, 1907. 



— 1907 b. An Analysis etc. II. Differences in Proportion in the Primordia. 

 Arch. f. Entw.-Mech. Bd. XXIII, H. 8, 1907. 



— 1907 c. An Analysis etc. III. Regional and Polar Differences in the Re- 



