Xo.<>:i3] 



NEOTENY 



351 



males. The sex ratios will vary greatly according to the 

 stress laid by the observer on the gross appearance of 

 the gonads (and it must be admitted that in early stages 

 the gonads of the two sexes are remarkably alike) or 

 upon the cytological evidence as it has heretofore been 

 interpreted. In larvae of 80-100 mm. length the sex ratio 

 is approximately 50-50 when based on the evidence pre- 

 sented by the gross appearance of the gonads; on the 

 other hand, the cytological criterion, as it has been inter- 

 preted, practically does away with males, while most 

 of the animals are apparently female. It is probably 

 due to this erroneous interpretation of cytological condi- 

 tions that such confusion reigns in the literature regard- 

 ing sex in anurans. 



The germ cells of larva? 45 mm. and over, both male 

 and female, are found in early maturation stages. Such 

 animals are about 8 months of age. Practically all of 

 the female cells are in the leptotene or pachytene stage. 

 In the females the leptotene and pachytene stages do not 

 persist for any length of time, but give place to the period 

 of growth, in which the cells with pachytene nuclei in- 

 crease greatly in volume, are invested by a follicle of 

 peritoneal cells, and become typical oocytes. Those cells 

 bordering the lumen of the gonad, are first to enter the 

 growth period, and by reason of their great increase in 

 size, fill up the cavity. Around the periphery of the 

 gland a ring of cells with leptotene and pachytene nuclei 

 persists, giving rise later to oocytes of a younger gen- 

 eration. Scattered through the gland are a few oogonia 

 with polymorphic nuclei. 



The female gland increases greatly in size due* to the 

 growth of the oocytes, becomes much infolded and convo- 

 luted by inequalities of growth, thus taking on the char- 

 acteristics of the typical ovary of the adult. These typi- 

 cal ovaries are to be found in larvae over 80 mm. long. 

 The gonads probably persist in this condition for several 

 years after metamorphosis, the oocytes growing very 

 slowly. According to the observations of Hertwig and 

 others, the females of Bona tcmporaria and Bana escu- 



