364 INEZ WHIPPLE WILDER AND ELIZABETH BARRETT PEABODY. 



Typical Larval Stage. 



With the younger stages, macroscopic evidence could be relied 

 upon still less for sexing, although normal ovaries are easily 

 recognizable if the growth period of the ova has been well entered 

 upon, and such normal female gonads packed with growing ova 

 of approximately uniform size have been distinguished macro- 

 scopically in larvae as small as 25 mm. in length, though our per- 

 centage data (p. 8) did not include individuals under 27 mm. in 

 length. The difficulty in sexing lies in the uncertainty as to the 

 presence of male elements in gonads in which the ova are few in 

 number but unmistakable. We have not as yet examined micro- 

 scopically large numbers of gonads of young larvae. However, in 

 looking over our laboratory sets of serial sections of larvae col- 

 lected in September or early October, ranging in length from 17 

 to 25 mm. and presumably about 12 weeks old, we find that while 

 a few of them show a condition which might be considered as 

 sexually indifferent in that the gonads are made up of typical 

 primordial germ cells, each with its investment of follicle cells, 

 arranged in single rank about a central cord, a larger number of 

 those examined, including some of the smallest individuals, show 

 practically all of the germ cells in early maturation stages (lepto- 

 nene and pachytene) or as growing oocytes. Such an individual 

 seems to us to be a female, since other individuals show gonads 

 made up of more numerous, smaller germ cells grouped in such a 

 manner as to suggest at once the incipient lobules of a typical 

 testis. In such gonads the germ cells show no maturation phe- 

 nomena, although mitosis is ocasionally seen. For the most part 

 the nuclei are either polymorphic, or in rounded form with one or 

 more conspicuous nucleoli. As we have very few data as to the 

 condition of the gonads the following spring, we can only express 

 here our tentative opinion that this species, in spite of its pro- 

 longed larval life, exhibits no such early larval maturation of male 

 germ cells synchronously with that of the female germ cells, as has 

 been described by Swingle ('21) for Rana catesbeiana. 



To push our power of diagnosis of sex and recognition of pos- 

 sible hermaphrodites back into these early stages demands as a 

 basis, not only a careful and thorough cytological investigation of 

 the origin and differentiation of the germ cells such as that of 



