442 INTERNAL SECRETIONS 



It is true that the castrated hen assumes the plumage and the 

 spurs of the cock; but the castrated cock-feathered hen does 

 not resemble the normal cock, but the capon. On the other 

 hand the castrated cock does not assume the characters of the 

 hen, and whereas cock-feathering is very often to be found in 

 old hens, hen-feathering in cocks is a very rare phenomenon. 

 So it is clear that there is no mutual transformation of one 

 sex into the other in birds after castration, but only an 

 assumption of a common or neutral form by the male and 

 female; this common form is very like the male one. 



Several authors such as Tandler and Kelley (igio) , Tandler 

 and Gross (1913, pp. 29 and 133) and Kammerer (1912) have 

 discussed the occurrence of the asexual type in relation to 

 phylogenetic questions also. But here we shall confine our- 

 selves to the embryological side of the problem. 



Basing his position upon observations on castrated birds, 

 Pezard suggested that in birds there is a "neutral" form 

 also during embryonic development. 



In accordance with the view held by Tandler and his 

 co-workers and by Pezard, I suggested (1917, 1918 a) that during 

 embryonic development the soma in mammals and birds is 

 asexual, and that differentiation of male and female sex 

 characters begins only after the differentiation of the hormone- 

 producing sex gland has taken place. Such a suggestion 

 implies that the male and female hormones have a different 

 or, as I said, a sex specific effect. The experiments of Steinach 

 with feminization and masculinization, which have been 

 fully confirmed by the numerous observations of Athias, 

 Brandes, Goodale, Lichtenstern, Lipschiitz, Minoura, Moore, 

 Pezard, Sand and Zawadowsky, leave no doubt about this 

 latter point. It cannot be denied that the sex gland also 

 produces hormones which have no sex specific effects; the 

 experiments of Steinach and Meisenheimer on the frog, and 

 certain observations on castrated hens as related in 

 Chapter IX. seem to prove this. But the fact that the sex 

 glands produce hormones which are able to modify the 

 organism in a sex specific manner must be regarded as 

 definitely established 



The view I put forward on this question in the first edition 

 of this book has been discussed and much contested by different 

 authors. But on the other hand some authors, who base their 



