THE AMPHIBIA OF OKLAHOMA 



substantiates field observations in several pools during which I have watched 

 social behavior during the formation of great feeding aggregations, often 

 when nothing could be found which might have started such an aggregation. 



Experiment 4. This was designed to determine definitely how effective 

 bottom materials from pools of types 1 and 2 may be as a total food source 

 for Scaphiopus hurterii from the time of total absorption of the deutoplasm 

 of the zygote till just after metamorphosis. 



Source of materials: On August 21, 1947, I had collected a portion of 

 the dried bottom of Pool C. This had been kept in a closely tied canvas bag 

 till used. A similar sample of the dried bottom of Pool A was collected on 

 April 17, 1948, at the end of the first evaporation cycle of the season here. 

 The sample from Pool A had no obvious fibrous materials but did have large 

 numbers of dead tadpoles. On the night of May 10, 1948, a mated pair of 

 S. hurterii was observed in Pool F. They were left undisturbed. The next 

 forenoon I visited the pool and found that one clutch of eggs had been laid. 

 Some of these (now young embryos, of course) were collected and taken 

 alive to the laboratory. They were immediately placed into a fingerbowl of 

 clear tap water and set aside. They eventually hatched normally but were 

 never fed prior to setting up the experiment. 



On May 17, 1948, the experiment was set up as follows: Two clean 

 aquaria, each approximately 37.5 X 14.5 cm. inside measurement were 

 labeled A and B. In A, the soil sample from Pool C, ten of the young tad- 

 poles, and tap water to a depth of 10 cm. were placed. In B, the treatment 

 was exactly the same except that the bottom sample from Pool A was used. 

 A larger quantity of bottom materials was used in A than in B because it was 

 suspected that the dead tadpoles in the latter might be more effective than 

 the materials without them in A. The tadpoles used were so uniform in size 

 and shape that no differences were discernible to the naked eye. Accordingly, 

 only one, taken as typical of all, was measured. This had a head-body length 

 of 5 mm. and a tail length of 10 mm. ( 15mm. total length). All growth from 

 the egg stage must have come about by utilization of deutoplasm and absorp- 

 tion of water (with the unlikely exception that the egg jellies might have 

 been utilized). At the end of two days the water in each aquarium was clear. 

 Most of the tadpoles in both aquaria were thinner than before and moved 

 slowly. They apparently were not feeding (none had been seen to do so). 

 But a few in each aquarium were larger, more active, and round bodied. 

 These were at least twice the bulk of their fellows but did not equal the size 

 of tadpoles of the same clutch left undisturbed in Pool F. 



The next morning (three days from the start) many of the tadpoles 

 had increased surprisingly in size. Some details set down in notes: "A. Water 

 temperature = 23° C. All tadpoles, larger than yesterday and with little 

 variation in size. All active but now look to be well fed. Several, feeding on 

 the bottom mud and all appear to have ingested such materials (known from 

 the color of the intestine seen through ventral body wall)." There was no 

 social behavior. "J^). Water temperature = 23° C. One tadpole is small, 

 weak, and inactive at the surface. Another is active, round bodied, and about 



IIO 



