THE AMPHIBIA OF OKLAHOMA 



Mean 



8.8 



19.8 



Because of changes at metamorphosis in the B series but not in the A 

 series, the figures somewhat belie the really great difference between the 

 two. It is to be noted, however, that even after the shrinkage in size which 

 is a normal part of transformation, those of the B series exceeded those of 

 the A series by approximately 2.7 mm. (mean) in head-body length. 



As a further minor check on the bottom materials, large amounts of 

 which were still present in each ac]uarium (the dried tadpoles in B had dis- 

 appeared) I changed the water in both A and B, bringing them to the same 

 level. Then I distributed the tadpoles from A in the two as follows: In A 

 were placed Nos. 1, 2, and 3 (ll.S-j- ^ mean length); in B, Nos. 4, 5, and 6 

 (mean = 15.0 mm.). No. 7 was preserved to illustrate conditions at the time. 



On June 16, they were examined briefly. Little change was noted; but 

 the next day those now in B seemed larger than those in A. In the former 

 but not in the latter, dorsal markings and hind limbs were developing, indi- 

 cating the approach of metamorphosis. 



On July 2, the experiment was terminated. Conditions were as follows: 



B. Two tadpoles were present: They measured 11.0, 16.0, and 27.0; 

 and 12.5, 12.5, and 25.0 mm. (head-body, tail, and total lengths, respectively). 

 In the first, the forelegs had just come through, in the other they appeared 

 just about to do so. The tail fin had not yet shrivelled. 



A. One tadpole (measuring 13.0, 14.0, 27.0 mm.) was present. This one 

 was about like the second one in B. 



From this experiment the following conclusions were drawn: 



( 1 ) Bottom material from some former pools may serve as an adequate 

 total external food supply for development of tadpoles of S. hurterti. 



(2) The materials from some poolsites (at a given time) are more ade- 

 quate than others. 



(3) Both growth rates and developmental rates depend at least in part 

 on the nature of the food available, i.e., on the nature of the bottom materials. 



(4) Individual rates, both of growth and development, may vary in the 

 same environment and with an abundance of adequate food. Presumably 

 this is due to the differential behavior in feeding among individuals. 



The experiment indicates strongly but does not prove that dried tad- 

 poles in the bottom mud if present in sufficient bulk may ( 1 ) contribute to 

 the speed of both growth and development, (2) contain substances necessary 

 for quick metamorphosis, and perhaps (3) prevent cannibalism during meta- 

 morphic stages. > 



112 



