No. 644] TRANSFORMATION OF SEX 



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cells of the so-called sexually intermediate tadpoles and 

 compared them with the cells of Bidder's organ in male 

 toads, is at once struck by the remarkable similarity in 

 their origin, development, structure and fate in the two 

 groups. They are identical. The crux of the problem 

 is the nature of Bidder's organ in male Bufonidae and 

 of the oviform-like cells of the pro-testis. The advocates 

 of sex transformation have assumed that such cells are 

 undoubtedly female, but no proof has ever been advanced 

 that they are. Their ultimate fate is the same as that 

 of the first year spermatocytes in the bullfrog tadpole — 

 degeneration (see Plates 1 and 2). The sex-transforma- 

 tionists have been misled by the idea that everything 

 superficially resembling an oocyte is necessarily such, or 

 that any cell in tadpoles and first-year animals undergo- 

 ing the early growth stages, leptotene, pachytene, etc., is 

 to be regarded as female. These are fallacious criteria. 

 Enormously hypertrophied oocyte-like cells which have 

 passed through the early growth stages and entered the 

 germinal vesicle " period so characteristic of oocytes, 

 occur as normal features of the male sexual cycle of 

 certain animals, e.g., myriapods (Figs. 5-8). These 

 animals were at first regarded as hermaphrodites by 

 Blackman (1905, Btill. Mus. Comp. Zool., Harvard, Vol. 

 XL VIII, no. 1) who found upon examination, however, 

 that these " oocytes " were in reality spermatocytes of 

 giant proportions, and developed into spermatozoa. The 

 writer has examine<i some of Professor Blackman 's ma- 

 terial and the oocyte-like character of the male sex-cells 

 is remarkable. In the material examined these cells prac- 

 tically fill the gonads. Firket, 1920, working on the chick 

 embryo, describes and figures spermatocytes undergoing 

 oviform degeneration, i.e., enlarging to such an extent 

 as to resemble oocytes. There are many other cases re- 

 ported in the literature. How does Witschi know that 

 the transitory oocyte-like cells he describes in the future 

 male tadpoles or so-called hermaphrodites, are female 

 cells and not senescent organ of Bidder cells occurring 



