GROWTH RATHS AND SliXUAL MATURITY 



groups. Breeding had occurred in the many pools over and over again during 

 this spring. However, in one place (Sta. A), the breeding site hati obviously 

 been used but once, and all of the tadpoles had metamorphosed within a 

 period of one week. Fortunately, the nearest pool to this at which breeding 

 was also successful was just less than two miles distant. Since our studies on 

 the movements of young toads had indicated that these toads congregate in 

 agricultural areas near the pool from which they emerged and since there 

 were several such areas available nearby, we assumed that any young toad 

 taken within a mile of this breeding site actually emerged from this pool 

 during the time indicated. Because of occasional mass movements, there is 

 probably some error introduced here, but that this is not great is indicated 

 by the fact that we always found very many more toads adjacent to cultivated 

 fields nearest the breeding pool (or in them) than elsewhere within the linear 

 mile usually covered by our collections. In traversing one mile of roadway 

 the night of August 4, for example, sixty-eight toads were collected, thirty- 

 two of which were taken adjacent to a cotton patch 0.2 miles in linear extent 

 along the road. Many such observations were made, always with consistent 

 results. 



The collections from this area furnish the data for Table III and Fig. 2. 

 On May 17, tadpoles in the water and metamorphosing toads on the bank 

 were present in about equal numbers. On week later. May 24, no tadpoles 

 could be found. May 21 was taken as the average date of emergence of toads 

 here. Collections were made about the pool as long as the toads remained. 

 Thereafter, toads taken within a mile south of it along roads and in adjacent 

 agricultural areas were assumed to have been produced in this pool. 



The young toads of the May 24 collection were very uniform in size and 

 grew but little during the following week. The next three collections showed 

 a much greater variability but indicated a period of rapid growth, which was 

 followed by a phase of decreasing growth rate coinciding with the appear- 

 ance of the first external indications of sexual differentiation. From this popu- 

 lation the first distinguishable males were taken on August 4, when they were 

 approximately fifteen weeks old (from metamorphosis). 



The last large collection of the year was on September 24 when both 

 males and females had reached a length of over 60 mm. However, the average 

 length of males at that time, as well as during the summer, exceeded that of 

 the females. It is possible, of course, that smaller, undiffereniated males were 

 designated as females because of the absence of the secondary sexual charac- 

 ters. The same condition persisted during the following spring, until collec- 

 tions were discontinued because of the inaccessibility of the area. Growth was 

 very slow during the second spring and the toads collected had not reached 

 full adult size by early June. 



The initially slow rate of increase in length followed by more rapid 

 growth and a final less rapid phase led us to attempt the computation of the 

 formula of the logistic curve most nearly expressing the observed relation- 

 ships. For the purpose of computation the data for September 15, September 

 19, and October 18 were omitted on account of the small numbers of indi- 



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