350 INEZ WHIPPLE WILDER AND ELIZABETH BARRETT PEABODY. 



criterion would obviate all possibility of the condition being given 

 the interpretation which Swingle has given to the oviform cells 

 which occur in Bidder's organ and in the larval testis (pro-testis) 

 of frogs. In carrying out our investigation we had in mind as 

 near an approach to this ideal as possible, and, having found 

 examples of the condition which to us seemed unquestionably 

 hermaphroditic in individuals of various stages up to transforma- 

 tion, we made a definite search for such cases among adult ani- 

 mals. As this search was rewarded by the discovery of one adult 

 in which the hermaphroditic condition was beyond question, al- 

 though the individual had not arrived at full sexual maturity, we 

 feel confident that our interpretation of our cases as true her- 

 maphrodites is correct and that the condition described cannot be 

 considered as " a normal but transitory embryological process." 



PERCENTAGE OF OCCURRENCE. 



The determination of the percentage of occurrence of her- 

 maphrodites with reference to that of males and females in Eurycea 

 bislineota is based upon the examination of the gonads of 1113 

 individuals ranging from the typical larval to the adult stage. 

 Wilder ('24) has shown that Eurycea bislincata is a form in 

 which the period before transformation is considerably prolonged, 

 covering from two to three years, although the structural changes 

 leading toward metamorphosis are inaugurated many months 

 previous to the actual transformation. The whole period from 

 hatching to transformation is subdivided on the basis of structural 

 changes into stages, the readily recognizable criteria of which, in 

 living individuals, are as follows : 



1. Postembryonic stage Yolk still present, intestine not fully 



formed. 



2. Typical larval stage Intestine fully formed ; no naso-lacrimal 



groove and no os tJiyreoidcum. 



3. Premetamorphic stage Open naso-lacrimal groove (in incipi- 



ent phase) ; os thyreoideum present; no vesicular glands in 

 the skin. 



4. Metamorphic stage Glands of skin appearing as tiny acinous 



vesicles (in incipient phase), becoming rapidly larger and 

 more conspicuous ; absorption of larval structures and de- 



