SEX STUDIES. XI 3 
To complete the more male end of the series we have studied 
two guinea-chicken hybrids, one raised on the Maine poultry 
plant and the other sent in for examination from the country. 
Their gonads appeared to be testes, but their behavior was 
indifferent. 
This series of birds has been studied from as many aspects as 
possible. The external secondary sex characters have been ob- 
served and many of the birds photographed to show any devia- 
tions from the normal. The behavior of the entire series has 
been carefully watched under various conditions and recorded. 
The birds were finally killed to study the anatomy and histology 
of the reproductive organs. The alimentary tract and associated 
organs were removed and a piece of the back with the entire 
urogenital system was put in McClendon’s fluid (10 per cent 
formalin, sugar, lime) to fix and harden. Then a careful dis- 
section was made of the urogenital system, and this was photo- 
graphed. The reproductive organs and ducts were then sec- 
tioned and studied histologically. Delafield’s haematoxylin and 
orange G were used for the general histological condition of the 
glands. The more special staining methods for studying inter- 
stitial cells have been considered in detail in study IX of this 
series. 
III EXTERNAL SEX CHARACTERS AND SEX BEHAVIOR 
Secondary sexual characters are very distinct and attain a 
relatively high degree of development in the domestic fowl. 
The cock bird is distinguished from the hen in a whole series of 
obvious respects. Of these the best known and most apparent 
are; (1) greater body size; (2) different shape of body and car- 
riage; (3) large comb and wattles; (4) presence of spurs; (5) 
presence of differentiated feathers in hackle, saddle and tail, (6) 
in some breeds dimorphism in color and pattern. There are 
many finer differences which can be recognized by the poultry 
expert. 
Presence of testes is supposed to cause the appearance of one 
set of these characters; presence of ovary, the appearance of the 
other. Actually in some ten years study of these characters in 
