ADAPTATIONS OF SUKVIVAL VALUE 



gnawing violently in the region ot the surface iilm. It was concluded that 

 these tadpoles had reacted positively to Hartz-Mountain I'ish Food when 

 hungry, and this fact supports the presumption that they would do so to other 

 organic materials. 



Simple experiments were devised to test these observations. 

 Experiment 1. Into each of two clean finger howls, exactly alike, were 

 placed 200 cc. of tap water from a single tap. After the dishes had stood lor 

 a few minutes to equalize temperatures (26° in each), ten tadpoles of S. hur- 

 ten'i were added to each. Ten minutes were allowed for stabilization. At the 

 end of this time the behavior of the tadpoles in both bowls was the normal 

 random swimming observed previously. The bowls were labeled A and B, 

 experimental and control respectively. To A, I added a sprinkle of the fish 

 food as before. In thirty seconds, one tadpole had found the food at the sur- 

 face. In forty-five seconds, eight were violently moving at the surface, the 

 other two attempting to feed at the bottom. In two minutes, one group of 

 three and another of four were attacking small particles at the surface with 

 violent movements. In six minutes, all were at the surface violently attempt- 

 ing to ingest the particles of food. Temperature ^25° C. at the end of the 

 experiment. 



In the meantime, the behavior in the control dish ( B) had not changed. 

 The normal slow random swimming had continued. Temperature = 25° C. 

 at the end of the experiment. 



It was concluded that the previous observation regarding the positive 

 reaction to this fish food was confirmed; these S. hurterii tadpoles reacted 

 positively to diffusion of chemicals and to physical disturbances, or both when 

 this lish food was added to the water containing them. 



Experiment 2. After the agitation had ceased in A, a small amount of 

 carmine powder (relatively insoluble in water) was sprinkled on the surface. 

 For the first few seconds, the tadpoles increased their movements, but withm 

 one-half minute all had settled to the normal, slow random swimming still 

 being maintained in B. None approached the carmine and there was no sug- 

 gestion of agitated movements as when comparable amounts of lish food had 

 been added. 



I then prepared two small squares of a porous cotton cloth cut to the 

 same size. On one I placed a small amount of carmine, on the other, a com- 

 parable amount of the fish food. Each cloth was then folded in the same 

 manner and tied with cotton thread from a single spool in such a manner to 

 form a bag of material. These bags were lowered simultaneously into bowl B 

 (the former control), so that the one was directly opposite the other and as 

 far away from it as possible. 



Within thirty seconds, eight of the ten tadpoles were attacking the bag 

 containing the fish food, all in the folded area nearest this material. Two 

 were attacking the carmine bag, but in a region of it well away from the car- 

 mine. In ten minutes all of the tadpoles were agitatedly attacking the bag of 

 fish food. At the end of fifteen minutes, two tadpoles were about the carmine 



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