INCUBATION OF THE EGG OF THE COMMON FOWL. 361 



Natural Position. Two nests containing an aggregate of 

 twenty-seven eggs were selected which were typical of the ex- 

 treme conditions. One of these was exceedingly flat, being on 

 the ground. The other, being in a box of straw, had a very con- 

 cave bottom, so that the eggs were crowded closely together ; 

 those at the periphery always rested on a sloping side. 



In each of these nests, the eggs were marked so that any 

 change of position was readily noted. A diagram of the nest 

 was made each day, showing the position of each egg and the 

 angle of inclination of its long axis. The sketches were made at 

 the time the hen was feeding. If she did not leave the nest, as 

 sometimes occurred, she was gently removed until the sketch 

 could be made. 



The angles were assigned according to the following method : 

 an egg whose long axis formed an angle of less than 10 with 

 the horizontal plane was marked o. If the long axis formed an 

 angle of more than 10 and less than 22 i/< it was recorded as 

 15. If the angle were more than 23*4 and less than 67^ 

 it was recorded as 45 degrees. While those whose angles Avere 

 more than 67^/2 were recorded as 90 degrees. It was found 

 to be impossible to register the exact angle without the expendi- 

 ture of much more time than the problem merited. 



In the nest with the flat bottom there was an average of less 

 than 10 per cent, of the eggs, in which the angle of inclination 

 exceeded 15. From this nest of twelve eggs eleven hatched, 

 giving a percentage of 91.7. 



In the second nest which was extremely concave an average 

 of 30 per cent, of the eggs showed an inclination of 45 or more. 

 From this nest containing fifteen eggs, thirteen hatched, giving a 

 percentage of 86.6. Three other nests on the ground were com- 

 pared with those in straw, but in these the percentage of chicks 

 hatched was about the same. These observations led to the 

 conclusion that the oblique position of the egg is a factor of little 

 or no importance in natural incubation. 



It should be added that in natural incubation, one very rarely 

 finds eggs so placed that the smaller end is uppermost. This is 

 probably the result of two mechanical factors. Those eggs at 

 the margin, when beneath the hen, assume an oblique position 



