43 



the same age. This is a very remarkable substantiation in a practical 

 way of our conclusion that since the air in the nest is very moist that in 

 an incubator must also be very moist for best results. 



But a comparison between Tables IX. and XII. will show that 

 although the humidity of the "wet" incubators with fanning- (which ap- 

 proximates to the correct humidity, the unfanned being- too high), is 

 slightly higher than that of the hens by the frame hygrometer (which also 

 approximates to the corect reading) still the selected eggs in the incubators 

 did not hatch nearly so well as those under the hens (all eggs set under 

 hens were selected). This being the case, we must conclude that some 

 vitalizing power (or powers) present with the hens was absent from the 

 incubators. 



Circulation in Nest. 



In the work on humidity thus far reported there lies almost hidden a 

 suggestion of a condition in a hen's nest not generally suspected, cer- 

 tainly not formerly suspected by us, which may ultimately be shown to be 

 that vitalizing influence, or at least one such. The reader will recall that 

 when the "egg" hygrometer was placed in the stoppered bottle, the sack 

 did not become dry even in three hours' time, and the humidity rose 

 almost to saturation. He will also recall, or by referring to Table No. 

 XI., he may again observe, that when the same hygrometer was placed 

 in a hen's nest it became dry in less than 40 minutes, and dry again in 

 about 45 minutes more, and partly dry a third time in 30 minutes, enough 

 water having thus evaporated to saturate the air at least four or five times 

 over, notwithstanding which the humidity in the nest remained constant 

 at only 70 per cent. These facts surprised me greatly at first, and they 

 suggested to my mind the idea of a fairly rapid change of air in the hen's 

 nest. To gain further light upon this point, the i( egg ,f and "frame" were 

 tested against each other in the room subject to free diffusion. The 

 results are given in Table No. XVI. : 



Table XVI. Comparison of Egg and Frame Hygrometer in Room. 



