March 1896.] GENEKAL AGRICULTURAL NOTES. 443 



few days. It may be mentioned in this connection that when 

 a hen, of necessity, leaves her nest each day, the eggs are 

 naturally subjected to a temporary refrigeration. 



In an experiment with the incubator, the eggs were cooled by 

 exposing them to the air daily for an hour and a half during the 

 whole course of incubation. This exposure retarded the period 

 of incubation for three days. The eggs which were thus exposed 

 became quite cold, and it required about 12 hours to bring them 

 back to 40° C. (104° F.), the temperature necessary for incuba- 

 tion. In this experiment 13 out of 16 eggs were hatched and 

 produced vigorous chicks. The incubator had previously been 

 employed for over a year without success. 



A second experiment, begun at 6 p.m. on the 17th of June, is 

 referred to by Madame Dieudonne as demonstrating that the 

 gradual heating of the eggs is no less essential than the process 

 of cooHog, 25 eggs which had been laid on the two preceding 

 and very warm days w^ere placed in the incubator and then 

 exposed to the air, as in the preceding case, but the w^eather 

 was much warmer, the thermometer registering 20° to 25° C. 

 (68° to 77° F.). When replaced in the incubator the eggs re- 

 gained the necessary temperature of 40° C. (104° F.) in about 

 two or three hours. This temperature was maintained until 

 the 10th of July, when the brood w^as hatched ; but although 

 the chicks pierced the shell, they were so w^eak that they died 

 before leaving the egg. 



It is interesting to note that the eggs on which a fowl is 

 sitting are not all at the same temperature, those which lie on 

 the outside being less warmed than the others. In this con- 

 nection, Mme. Dieudonne has observed a difference w^hich some- 

 times exceeds 6° C. (10 • 8° F.), and it is doubtless owing to this 

 cause that the hen instinctively changes the position of her eggs, 

 moving them from without inwards, and vice versa. 



With respect to these observations of Mme. Dieudonne, 

 M. Fouquet states, in a recent number of the Journal des Eco- 

 nomistes, that something analogous w^as published by M. Duclaux, 

 more than 25 years ago, regarding the egg of the silkworm, 

 whose life history may be divided into two periods w^Iiich are 

 separated from each other by an interval of cold. M. Duclaux 

 indeed showed that the action of cold was not only necessary 

 for the successful incubation of the egg, but that it could be 

 artificially employed so as to rear silkworms at a season in 

 which it would otherwise be impracticable to do so. The action 

 of cold having been shown to be necessary to induce the develop- 

 ment of the embryo within the egg, M. Duclaux further proved 

 that the eggs which are cooled artificially gave more healthy 

 products than those which are treated naturally, and in this 

 respect the action of cold would appear to have a beneficial 

 effect upon the incubation of the eggs. 



