BULLETIN 228. 



FACTORS IXFLUE^XIXG THE SIZE, SHAPE AND 



PHYSICAL CONSTITUTION OF THE EGG 



OF THE DOAIESTIC FOWL.* 



Maynie R. Curtis. 



In a study of the physiology of reproduction in the domestic 

 fowl one must soon recognize the fact that the number of eggs 

 produced is only a, rough measure of the reproductive activity 

 for the eggs produced are not all equivalent. The complicated 

 physiological processes involved in the production of an egg 

 are so influenced by both heredity and environment that they 

 result in quite unequal products. Eggs differ greatly in every 

 character. The scientific and economic importance of differ- 

 ences in size and quality is obvious. 



Investigations on inheritance in poultry have been in progress 

 at this laboratory for several years. In this work the eggs ol 

 about two hundred hens of one breed are handled individually 

 each season. The variation in these eggs is very great. The 

 four following facts in regard to it are apparent. 



I. The eggs of different individuals of the same strain vary 

 in size, shape, color and markings. 



* This paper is an abstract, setting forth the more important results 

 and conclusions, of an extended paper by the same author, published 

 under the following title : "A Biometrical Study of Egg Production in 

 the Domestic Fowl. IV. Factors Influencing the Size, Shape and 

 Physical Constitution of Eggs," in Archiv fuer Entwicklungsmechanik 

 der Organism (Roux). Bd 39, pp. 217, 1914. The three previous 

 papers in the series are : 



Pearl, R. and Surface, F. M. A Biometrical Study of Egg Produc- 

 tion in the Domestic Fowl. I. Variation in Annual Egg Production, 

 U. S. Department of Agr., Bur. of Animal Industry, Bui. no, pp. 1-80, 

 1909. • II. Seasonal Distribution of Egg Production. Ibid. pp. 81-170, 

 1911. III. Variation and Correlation in the Physical Characters of 

 the Egg. Ibid. pp. 171 — , 1914. 



