No. 633] 



NEOTENY 



357 



Bidder's organ in Bufo, and the oocytes-like cells of 

 anurans may not be true oocytes, despite their appear- 

 ance, but may be merely senescent cells, occurring in the 

 course of an abortive and degenerate larval sexual cycle. 

 Bidder's organ on this assumption is the vestigial remains 

 of a primitive sex gland functional when the Biit'miid;v 

 reproduced in the larval stage. The functional gonads 

 of present day toads represent recently acquired struc- 

 tures superimposed upon the phylogenetically older and 

 degenerate glands. 



In Rana catesbiana, a more primitive anuran type 

 than Bufo, the entire larval male gonad might with some 

 plausibility be compared to an organ of Bidder in which 

 only a few cells assume the oocyte character whereas the 

 remainder develop a little further, i.e., to the first matura- 

 tion anaphase, when they too go to pieces. The writer 

 suggests this view of Bidder's organ tentatively, and 

 pending further investigation does not regard himself as 

 irrevocably committed to it. The facts are suggestive, 

 and that is all that can be said at present. 



1918. Journal Exp. Zoology, Vol. 24, No. 3. The Results of Thyroid 

 Removal in the Larvae of Rana pipiens. 

 2. Witschi, Emil. 



1914. Archiv. fur mikr. Anatomic Bd. LXXXV. Experimented 



I>i.. Kntwi.-kl 



