APPENDIX II 



female respectively. The experiments obviously do not tell us 

 whether the substances that are produced in the embryonic 

 gonads, acting under natural conditions to induce the de- 

 velopment of the sex organs, are themselves hormones of the 

 steroid estrogen-androgen types which are effective in adult 

 physiology. For all we know at present, the embryonic 

 hormones may be chemically like or unlike the known estro- 

 gens and androgens. This query has implications too large for 

 further discussion here, leading us into the whole question of 

 the nature of the embryonic inductor substances and their 

 relation to growth-inducing and morphogenetic hormones. 

 (For a brief elementary statement of the theory of embryonic 

 inductors or "organizers," see G. W. Corner, Ourselves Un- 

 borUf New Haven, 194«4, pages 103-106; for a detailed dis- 

 cussion, see Joseph Needham, Biochemistry and Morpho- 

 genesis ^ Cambridge, England, 1946.) 



^^ParadoxicaV^ effects. It has frequently been observed, in 

 experiments with the sex-gland hormones upon embryonic 

 tissues, that higher dosages of the androgenic substances may 

 induce female rudiments to accelerate development in the 

 female direction, and there is evidence that estrogenic sub- 

 stances may sometimes act similarly upon male structures. 

 The studies of Burns (see the article cited above) have shown 

 that these so-called "paradoxical" effects occur in his 

 embryonic opossums only when the dosage of the hormones is 

 relatively high. By reducing the dose of the male hormone 

 Burns was able to limit its stimulative effects to male struc- 

 tures only, all the female structures being unaffected. We 

 may suppose therefore that the action of these hormones upon 

 embryonic rudiments is fundamentally sex-specific, and that 

 the "paradoxical" effects reported by various authors for a 

 number of animals are the result, in some way, of excessive 

 doses. 



Note 4 (page 111, line 33). Is the corpus luteum necessary 

 for segmentation of the egg and for implantation of the 



{ 267 ) 



