MATING BEHAVIOR OF THE WOOD PROG. 179 



occur in general only when the egg-laying is nearing completion, 

 though a few males were seen well up the bank and apparently 

 leaving the pond soon after the chorus had passed the climax 

 of its activity. The sperm ducts of some of these were examined 

 to see if perchance they might appear to be males which had 

 discharged their sexual products, but no consistent difference was 

 noted between those males leaving and the actively chorusing 

 males still on the pond. 



Most of the egg-laying, if the weather continues mild, occurs 

 within two days. The eggs are laid in enormous aggregations, 

 the bunches from the different females being crowded closely 

 together. In 1912 all the eggs in the Cut-off Pond were laid 

 within a radius of three or four feet. In 1911, and again in 1913, 

 there were two such aggregations in the pond. 



The indiscriminate trying by the males of every individual 

 encountered aroused the writer's interest in the mode of sex- 

 recognition. In an attempt to find the basis for sex-recognition 

 a number of experiments were tried, in each of which a frog was 

 fastened upon a light fishing line by hooking through the jaw 

 and used as a decoy among the chorusing males at the pond. 

 A long pole was used to hold and manipulate the decoy. The 

 live frogs so used, unless tired out, swam about and acted appar- 

 ently in a normal fashion, though the active females could not 

 be kept at the surface without considerable manipulation. 



The following notes were made on the spot, most of them 

 March 30, 1912, and illustrate characteristic behavior of the 

 mating frogs. 



Experiment i. A male which had been pairing with a female 

 in the laboratory all night was forcibly separated from its mate 

 and tried on the line but with no further result than to be ap- 

 proached or tackled by practically every male which happened 

 near him. 



Experiment 2. Placed a male paralyzed in the hind legs on 

 the line and kept it moving somewhat. While tackled many 

 times it was quickly released and in fact more often was merely 

 quickly approached and not actually touched. One male how- 

 ever took hold and clasped him for several seconds, perhaps 

 forty, but released him readily when I tried to simulate movement 

 of a female by moving the line to which it was attached. 



