Development of Parts Not Due to Local Relations 65 



esis becomes confirmed indirectly by a whole series of 

 other facts which Roux also has described and commented 

 upon with his customary carefulness. 



Natural or artificial headless monsters for example, 

 and in general all monsters lacking entire parts but other- 

 wise normal, prove that no formative action or reaction 

 is exerted by the head or by these other parts upon the 

 rest of the organism. 



They speak therefore in favor of a centroepigenesis 

 with independent networks of correlation in which it is 

 necessary to suppose that the formative action must 

 stream out entirely from a center toward the periphery. 

 In all these monsters of which some part is lacking, there 

 need be present only one part of the body namely the seat 

 of the central zone of development. 



Roux in his researches upon the formation of half- 

 embryos once observed, as an example of the disturbance 

 of correlations of mass by the absence of one embryonal 

 half, a lateral dislocation of the notochord and a corre- 

 sponding retardation of development of the dorsal part of 

 the endoblast lying near the median line as marked by the 

 semi-medulla and by the ventral parts. "It is an interest- 

 ing fact/' he remarks, "that the axial parts can be laid 

 down and developed with so considerable a shifting in 

 relation to one another. For this indicates further that 

 the development of many parts even of the main parts is 

 not included in the form as such; the embryo does not 

 live a formal life." 39 These facts would also confirm the 

 hypothesis of independent networks of correlation, the 

 displacement of whose material would not alter their 



39 Wilhelm Roux: Uber die kiinstliche Hervorbringung halber 

 Embryonen etc Virchows Archiv. Bd. 114. October 1888. P. 132. 

 Gesamm. Abhandl. Zw. Bd. P. 442. 



