3/O ALBERT C. EYCLESHYMER. 



As will be observed, the incubator was under better control in 

 the second experiment and the chicks hatched on the twentieth 

 and twenty-first days yet the percentage hatched was about the 

 same as in the first, not including in either case the eggs destroyed 

 in making the tests. While a more extended series of tests 

 would be highly desirable, one certainly does not widely err in 

 stating that the most favorable temperature within the egg cham- 

 ber is close to 1 02 - 1 03 F. the first half of the incubating 

 period and 103- 104 F. for the latter half. 



In any consideration of temperature, the fact must be kept in 

 mind that as the chick grows, it gives off more and more heat, 

 so that if an incubator of 200 egg capacity were entirely without 

 artificial heating, the temperature would be much higher than 

 that of the surrounding atmosphere ; it consequently follows that 

 less artificial heat is necessary during the later stages of incuba- 

 tion. The 1 02 - 1 03 in the earlier stages is largely artificial 

 heat, while the IO3-IO4 in the later stages would be the com- 

 bined animal heat, given off by the egg, and the artificial heat 

 supplied by the heat radiator. 



V. COOLING OF EGGS. 



How frequently the eggs should be cooled and for how long 

 a period, is a question of considerable importance. Not being 

 entirely satisfied with the data at hand, an attempt was made to 

 gather some information by actually watching a number of hens 

 from day to day. 



Natural Exposure. - - Six hens were observed throughout the 

 period of incubation and the results tabulated. It was found 

 that the average time the hen leaves her nest, during the first 

 fifteen or eighteen days is about thirty minutes. During the last 

 few days of the incubating period she rarely leaves the nest. The 

 longest time a nest was left exposed was an hour and twenty min- 

 utes, and the shortest time about twelve minutes. If the hen be 

 obliged to forage for food, she remains a much longer time than 

 when food is at hand. But one or two instances were noted in 

 which the eggs were exposed for much more than an hour. It may 

 be stated with a fair degree of certainty that the cooling of the eggs 

 is due to the necessity of obtaining food, and in no way funda- 



