206 THE AMERICAN NATURALIST [Vol. LVI 



the gonads does not exist and that evidence based on such 

 parallelism is worthless. 



In the normal males of adult Rana pipiens the Miil- 

 lerian ducts are remarkable for their size and degree of 

 development. They arise as cellular cords in the peri- 

 toneum at the time of metamorphosis and only acquire 

 full development long after transformation when they 

 come to resemble to a striking degree the oviducts of 

 females (Fig. 2). In the larva of R. pipiens the so-called 



transformation of females into males (degeneration of the 

 pro-testis and formation of the definitive testis) occurs 

 very early in larval life, before the Miillerian ducts ap- 

 pear, and in this species the ducts undergo practically 

 their entire development after the definitive testis has 

 formed. In other words, while subjected to the influence 

 of the fully formed testis and its ripening sex products 

 the ducts undergo the most marked development known 

 in the males of any anuran species. ^Moreover, in Rana 

 cafesbeiana, where if we accept Witschi's interpretation 

 of femaleness, the so-called transformation of female in- 



