ANIMAL PRODUCTION. 171 



most such birds have also produced one or more when they were young pullets. 

 There has been no bird in the experiment station flock with which the laying 

 of double-yolked eggs was ' habitual ' although there are some which have 

 produced several such eggs. 



" The production of an egg with two or three yolks represents the extreme 

 of rapid egg production, other forms of which are found in the production of 

 two eggs united by a membranous tube; two eggs at the same time; two eggs 

 at different times on the same day, and a daily egg production where the eggs 

 are laid earlier on each successive day. The two yolks of a double-yolked 

 egg may have all the egg envelopes in common, indicating that they have passed 

 the entire length of the duct together; or each may possess one or more sepa- 

 rate envelopes. There are also all the possible intermediate forms indicating 

 that the two yolks in a common shell may unite at any point between the 

 mouth of the funnel and the isthmus. When two eggs come together after 

 the first has entirely passed the anterior end of the isthmus the result is the 

 production of two eggs at the same time. 



" Vai'ious disturbances of the processes of egg production may bring two yolks 

 together in the oviduct. Double-yolked eggs evidently do not always repre- 

 sent simultaneous ovulations. The assumption is simultaneity or abnormally 

 close succession of ovulations is necessary to account for the production of a 

 succession of double-yolked eggs or of a double-yolked egg immediately follow- 

 ing a long series of normal daily eggs. 



" The double-yolked eggs contain more albumin and have a heavier shell than 

 single-yolked eggs, and in triple-yolked eggs these parts are heavier than in 

 double-yolked eggs. Yet these parts do not increase in direct proportion to the 

 Increase in the weight of yolk. That is, the percentage of albumin and shell 

 is less in double- than in single-yolked eggs and is still smaller in triple-yolked 

 egg.s. The yolks of the multiple-yolked eggs of mature birds are not con- 

 sistently smaller than the yolks of the normal eggs produced during the same 

 period: Multiple-yolked eggs are longer in proportion to their breadth than 

 the normal eggs of the same individual." 



Previous studies have been noted. (E. S. R., 26, p. 670). 



The bacteriology of the hen's egg, with special reference to its freedom 

 from microbic invasion, L. F. Rettger (Connecticut Storrs Sta. Bui. 75 {1913), 

 pp. 191-213). — Bacteriological tests were made of more than 10,000 eggs of 

 different ages under various degrees of incubation. 



Yolks from fresh eggs showed a positive test for bacteria other than Bac- 

 terium puUorum of 9.5 per cent. The yolks of artificially incubated eggs showed 

 2.75 per cent positive test during the first week of incubation, 1.3 per cent the 

 second, and 3.6 per cent the third week. 



The small percentage of positive results for eggs which have been incubated 

 from 1 to 3 weeks is considered a noteworthy fact. A more exact uicthod was 

 employed in testing the yolks of fresh eggs and in this case the test was re- 

 duced to 3.86 per cent. It is believed that even this test is in all probability 

 considerably above the actual figures, could accidental invasion of bacteria in 

 the tests be entirely prevented. The tests with eggs incubated 1 and 2 weeks 

 indicate that fertilized eggs do not become more subject to bacterial invasion 

 of the yolk than the infertile. 



In examinations of the whites of 582 eggs only 1.2 per cent gave positive 

 bacteriological results, although many of the tests were made during the sum- 

 mer months. No Bacterium puUorum, the organism of white diarrhea, was 

 detected in the white, although it was recovered from the yolks. Undoubtedly 

 there was some contamination in these tests and it is believed to be safe to 



50128°— No. 2—14 6 



