266 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



of a quantitative rather than of a qualitative character. We have here to deal, 

 as in all vital phenomena, with a quantitatively varying interaction between 

 genetically determined, inherent factors and inner or outer environmental 

 factors. It must be borne in mind that inner environmental factors may also 

 be genetically determined. 



The relations between inductor and recipient substratum may vary in dif- 

 ferent cases. As Mangold points out, ordinarily an organizer transforms the 

 substratum in such a way that both organizer and substratum form one whole, 

 which tends to reproduce the organism in which this transformation occurs. 

 This condition Mangold designates as "complementary induction." But, in 

 other cases the organizer gives rise in the host tissue to the formation of 

 structures which do not fit into such an organization, as when double or other 

 abnormal structures develop. Such an occurrence Mangold calls "autonomous 

 induction." This is found only under abnormal conditions ; for instance, when 

 the age and stage of differentiation differ very much in inductor and sub- 

 stratum, so that the typical sequence of interactions is disturbed. Or, in other 

 cases an autonomous induction may take place in case of xenoplastic trans- 

 plantation when the organismal differentials of host and transplant are so 

 strange to each other that a complementary result becomes impossible. 



These observations present an interesting parallelism to those found after 

 transplantation of adult pieces of organs or tissues in primitive classes of 

 animals. Here also the transplant may unite with the host in an integrated 

 manner, leading in the end to the formation of a normal individual. We may 

 assume that under these conditions a tissue acting as organizer causes com- 

 plementary induction ; but if the surfaces of contact do not fit each other, 

 or if the organismal differentials are too far removed from each other, then 

 an autonomous induction takes place in the embryo, while in the adult the 

 transplant becomes absorbed or is cast off and the host tissue may undergo 

 regenerative growth processes. 



As to the effect of the relative size of organizer and recipient tissue, 

 Bytinski-Salz has observed that within a certain range the larger the organizer 

 piece the greater its effectiveness, other conditions being equal. Quite recently 

 Schotte carried out some experiments which, while made for other purposes, 

 also have some bearing on this question. He transplanted large portions of 

 the ectoderm, including the presumptive medullary plate, from young gastrulae 

 of Hyla crucifer to the face region of Amblystoma punctatum, the former a 

 relatively small and the latter a relatively large organism. Under the influence 

 of the large quantity of organizer for mouth organs which was present in the 

 face region of the Amblystoma host, mouth organs formed in Hyla skin, 

 which were typical suckers with Hyla character, but they were three times 

 as large as they normally are in Hyla. The number of cells which entered into 

 these suckers was likewise about three times greater than is normally observed 

 in Hyla embryos. Similar results were obtained with the induction of other 

 organs, such as lenses, nasal placodes, ear vesicles and mouth organs. We may 

 assume that the larger quantity of organizer material present in certain regions 

 of Amblystoma induces formation of correspondingly larger organs in the 



