EXPERIMENTAL MORPHOGENESIS 107 



or " causes " of morphogenesis by shortly adding, more on 

 account of its factual than of its logical interest, that the 

 phenomenon of the determination of sex, 1 according to the 

 latest researches, seems to depend on cytological events 

 occurring in the very earliest embryonic stages, say even 

 before ontogeny, and not on formative stimuli proper 2 : it 

 seems, indeed, as if the sexual products themselves would 

 account for the sex of the individual produced by them, 

 particularly if there were differences in their chromatin. 3 



8. THE MORPHOGENETIC HARMONIES 



Let us now turn again to considerations of a more 

 abstract kind : we have become acquainted with some 

 morphogenetic interactions among the parts of a developing 

 embryo ; and, indeed, we can be sure that there exist far 

 more of such interactions than we know at present. 



But it is far from being true that the development of 

 each embryonic part depends on the existence or develop- 

 ment of every other one. 



On the contrary, it is a very important and fundamental 

 feature of organogenesis that it occurs in separate lines, 



1 A full account of the present state of the subject will be found in 

 Morgan's Experimental Zoology, New York, 1907. 



2 But there certainly exist many formative relations between the real 

 sexual organs and the so-called secondary sexual characters. Herbst has 

 given a full analytical discussion of all that is known on this subject ; but 

 the facts are much more complicated than is generally supposed, and do not 

 lend themselves therefore to short description. See also Foges, Pflilgers Arch. 

 93, 1902. 



' It seems that in some cases (Dinophilus, certain Arthropods) the sexual 

 products are invariably determined as " arrenogeunetic " or as "thelygen- 

 netic" (Wilson, Journ. Exp. Zool. ii. and iii. 1905-6), whilst in others 

 (Amphibia) the state of maturation or " super "-maturation determines the 

 sex of the future organism (R. Hertwig, Verh. D. Zool. Ges. 1905-7). 



