196 THE AMERICAN NATURALIST [Vol. LVI 



turation cycle is cut sliort by the cells early becoming 

 senescent and undergoing oviform degeneration i.e., by- 

 pertTophy to such an extent as to superficially resemble 

 oocytes. This oviform degeneration occurs to an even 

 more marked degree in the progonad of the toad which 

 has a still shorter larval-life, e.g., in Bidder's organ. In 

 male anurans the entire pro-testis or larval gonad is the 

 homologue of the male organ of Bidder in Bufo. 



The pro-testis of the short larval-lived frogs has been 

 misinterpreted as an ovary owing to the oviform-type of 

 degeneration characteristic of many of its senescent cells, 

 and hence tadpoles are said to develop first as females, 

 fifty per cent, later transforming into males. The normal 

 embryological process by which the definitive testis de- 

 velops as a central axis through the degenerating pro- 

 testis or larval Bidder's organ, has been described by 

 Witschi as the transformation of female tadpoles into 

 males. In R. catesheiana, where the larval life is pro- 

 longed over two years, the true nature of the pro-testis 

 is revealed, for relatively few of the cells are of the ovi- 

 form type and all transition stages between such cells 

 and normal spermatocytes occur. The evidence pre- 

 sented by this material will be published in due time, and 

 is too clean-cut to admit of any doubt that the entire 

 larval gonad of male anurans is simply an embryonic 

 male sex gland rudiment and not a temporary ovary. 

 Witschi 's Fig. 6 (this journal, Vol. LV), which he sup- 

 poses is an ovary transforming into a testis is simply a 

 transition stage in the development of the definitive testis, 

 and degeneration of the pro-testis or Bidder's organ in 

 a short larval-lived frog. Compare his Fig. 6 with Fig. 

 1 of this paper and note how the true male character 

 of the cells of the pro-testis comes out in Rana cateshei- 

 ana tadpoles. 



When the facts are considered it is evident that the 

 transitory gonadic rudiment of male frog larvae is an or- 

 gan of Bidder which degenerates and is replaced by the de- 

 finitive gonad. Any one who has studied the oviform-like 



