BEHAVIOR OF VERTEBRATES 443 



experiments. His chief argument is that the spawning migra- 

 tion is not actuated by any sexual instinct, but is an adaptive 

 change which has as its end the obtaining of optimal develop- 

 mental conditions for the young. It is conditioned solely by 

 hydrographic phenomena. 



Thauzi^s ''^ gives the record in detail of the homing pigeons 

 released by him at Geneva when the Sixth International Congress 

 was in session. Birds belonging to the three cities, Versailles, 

 Gueret, and Gannat were used. None of them had flown from 

 Geneva previously. The birds from Versailles had been trained 

 toward Brest, those of Gueret towards Amsterdam, and those 

 from Gannat, towards Macon. 



Versailles: 24 birds were released August 6: two returned 

 the same day at about 5 45 P. M. ; nine returned August 7 at 

 dift'erent hours; by the loth of August all the birds had returned. 



Gueret: 38 released at 7:15 A. M., August 6; two returned 

 the same day a little after noon. The rest returned on the follow- 

 ing morning. 



Gannat: eight pigeons w^ere released at 7 :2o A. M., August 6. 

 None returned the first day. On the 7th of August three returned 

 in the morning; one on the 8th, and one each on the 9th, nth 

 and 12th. One had failed to return by the 17th. 



Hachet-Souplet "- reports a set of experiments made upon 

 pigeons reared in movable cotes. The pigeons were taken 

 from the wagon at a point A and placed in a basket. The 

 outside appearance of the wagon was of course familiar to the 

 birds. The "traveling cote" was then driven to a point B, 

 5 km. from A. The pigeons were released. They quickly 

 found the cote at B. The experiment was then repeated with 

 the distance between the two points increased to 10 km. Care 

 was always taken to place the wagon, covered with a large 

 drapery, in an open place. The birds invariably found it at 

 this distance. The moment 10 km. is exceeded, a decrease 

 in the number of returns is noticed. No returns were obtained 

 from distances greater than 12 km. 



Now, by proceeding in another way, the birds may be made 

 to return to the wagon from much greater distances. On leav- 

 ing the point A, two birds are attached to the outside of each 

 wagon by a cord in such a way that as the wagon travels they 

 can view the surrounding country. The string permits the 



