Anomalies in the Genital Organs of Toads. 165 
rule, segregated into one or several masses which can be seen under 
a low magnification before the gland is sectioned, and they have 
very distinctive characteristics that distinguish them from normal 
ova; in Rana, according to Schmitt-Marcel, the large cells are scat- 
tered throughout the sex-gland, and they appear in every respect like 
normal ova. 
Schmitt-Marcel offers no suggestion as to how or why, in an 
individual in which the female sex is already determined, the pri- 
mordial germ-cells can change the course of their development and 
subsequently alter the sex of the individual. If this phenomenon 
is of common occurrence in young Rana temporaria, then it would 
seem as if some clue might be’ obtained as to the causes which deter- 
mine sex in this species if an extensive series of experiments was to be 
made with young individuals that had recently completed their meta- 
morphosis. 
Except in rare cases, the sex of young toads in which anoma- 
lies appear in the genital organs can readily be ascertained, since, 
although the primordial germ-cells may appear alike in both sexes 
at this time, the ovary has a central cavity which is lacking in the 
testes. There are, therefore, no young toads that can properly be 
ealled “intermediate forms,” as each individual is at this time defi- 
nitely male or female, no matter how many cells appearing like 
rudimentary ova may be present in the sex-glands. 
The development of the genital organs must be considerably 
slower in Rana temporaria than in Bufo lentiginosus, since in the 
former species it is impossible to ascertain the sex of many indi- 
viduals until they are nearly a year old. As according to Schmitt- 
Marcel the germ-cell tissue which spreads throughout the sex-glands 
in these intermediate forms is still in an indifferent state I can see 
no valid reason for the assumption that such forms were originally 
females. In Bufo, as far as I can judge from the number of cases 
(about 75) that have come under my observation, large cells with 
the characteristics of rudimentary ova appear somewhat more com- 
monly in the genital glands of young males than in those of young 
females. Assuming that a similar condition exists in young Rana 
temporaria, one readily accounts for the fact that the great majority 
