SEX DETERMINATION AND SEX DIFFERENTIATION 229 



females with engrafted testes showed a tendency toward male differ- 

 entiation, especially in instincts. These experiments have been 

 largely confirmed by C. R. Moore. 



In birds it is of interest to note that practically complete reversal 

 of secondary sexual characters may be induced if young females are 

 entirely deprived of the ovary. The condition is described by L. V. 

 Domm as follows: 



"The larger percentage of our birds have assumed additional male 

 characters following removal of the ovaries, until they are practically 

 complete replicas of the male, and, to those not familiar with their 

 history, they are regarded as unmistakable males. Thus we find that 

 they assume the complete male plumage, spurs grow as they do in the 

 normal cock, head furnishings increase in size until they can not be 

 distinguished from those of the normal male. 



"Other birds in the pen regard them as males and when a strange 

 cock is introduced they fight as would other cocks, very frequently 

 assuming the initiative, some of them having been observed to come 

 off victorious in such a combat. Many of these birds crow regularly. 

 When aroused by a disturbance, it was found that their reaction is 

 very similar to that of the male; the sounds they make, together with 

 their reaction on such occasions, reminds one very much of the young 

 male just prior to maturity. 



"One set of experiments may be mentioned as an example: Out 

 of the one lot of fourteen females of the same hatch, one was kept as 

 control and thirteen were operated upon between the ages of six weeks 

 and six months; twelve of these have developed all the characteristics 

 of the male mentioned above, some being completely cock-feathered, 

 while the others are fast becoming so. The other one of the thirteen 

 is very capon-like in appearance except perhaps for size and can not 

 be readily distinguished from her capon brothers by those not know- 

 ing her history. This bird has assumed complete male plumage, is 

 developing spurs; but the comb, wattles and earlobes are pale and 

 small, resembling those of the capon. 



"In some of our cases individuals which have assumed more or 

 less complete male characters as concerns head furnishings, plumage 

 and spurs, are reverting toward the female type as shown by the female 

 type of plumage reappearing. 



"Our results indicate that the female in the brown leghorn fowl 

 has many potentialities of the male, which are normally inhibited by 

 the presence of the ovary, and that these potentialities can assert 



