THE MIT AT ED GENE 189 



experiments, i.e., in a case where the normal genie action has 

 been replaced by another one. Goldschmidt (1931c) studied 

 the details of the transformation of a testis into an ovary, and vice 

 versa. He found that the facts were not in favor of the assump- 

 tion that the determining processes went on in the individual 

 cells. He made it probable that the balance of the sex genes in 

 this case either stimulated the sheath of the ovary to produce a 

 hormone acting upon the whole gonad in transforming it into a 

 testis; or, on the contrary, stimulated a group of cells in the 

 attachment point of the vas deferens to the testicular compart- 

 ments to produce a hormone, transforming the testis into an 

 ovary. 



From the study of intersexuality in Lymantria, many more 

 cases may be derived. It is frequently found that an organ that 

 has been developed first male and ought to become female later, 

 or vice versa, after the turning point continues with its male 

 differentiation, when that has once started, if no female homolo- 

 gous part exists into which it could be transformed. For 

 example, in male intersexuality the valvae and penis of the genital 

 armature may fully differentiate after the turning point; whereas 

 the uncus is transformed into its female homologon, the labiae. 

 From this we may conclude that at a certain stage of development 

 the whole Anlage is determined by a hormone-like substance, 

 produced by genie action; furthermore, that the action of this 

 hormone has the maximum effect after a definite time of activity, 

 just as in Kuehn's experiments (page 185) 24 hr. presence of 

 hormone producer sufficed for full effect. It might be mentioned 

 incidentally that here also is found the explanation for the special 

 type of intersexes with both ovaries and testes produced in 

 Drosophila by Lebedeff (1934). A similar conclusion may be 

 derived from recent experimental work by Bytinsky-Salz (1933) 

 and Bodenstein (1936). Salz found that certain species hybrids 

 of Lepidoptera are unable to develop beyond a certain stage. 

 The same organ transplanted to a pure species will be induced to 

 behave like the host's organs. This looks like a kind of hormonie 

 control of differentiation. 



From the standpoint of experimental embryology, the facts 

 just mentioned would be called an induction, and the application 

 of the hormone concept is not absolutely necessary though rather 

 probable, if cases like the gonad transformation are studied. 



