Study op Seliictions for Size, Shape, and CotOR of Hens' Eggs 197 



results obtained in a study of the number of leaves to a whorl in 

 Ceratophyllum made by Pearl, Pepper, and Hagle,' and in a later study 

 for egg shape made by Pearl (1909). Similar variations in sparrows' 

 eggs have been observed also by Pearson (1902 b). 



Stewart and Atwood (1909) report that chicks hatched from pullets' 

 eggs are not so large nor so vigorous as those hatched from the eggs of 

 hens two and three years old. Atwood (1914) mentions this fact as 

 showing that chicks hatct ed from larger eggs are larger and more vigorous 

 than others. It would seem that there is danger here of attributing 

 any possible defect of the embryo due to the inamaturity of the parent, 

 to the smaller size of the agj, which also is due to the immaturity of the 

 parent. The writer does not see proof that a smaller egg produces a 

 smaller and weaker chick irrespective of the maturity and condition of 

 the parent. 



Pearl and Curtis (1916) found thai the two characters size and shape, 

 as measured by weight, length, and breadth, show different degrees 

 of variability, ranging from the most variable to the least variable in 

 the order named. Pearl and Curtis were able also to strengthen their 

 previous conclusions that the index and the weight are negatively cor- 

 related. They found that dwarf or abnormal eggs do not occur more 

 frequently at the beginning or at the end of the Htter than at other times. 

 During the eight years previous to their study, 5.15 per cent of all the 

 birds kept at the Maine experiment station produced one or more dwarf 

 eggs, and only 3.5 per cent of this 5.15 per cent produced more than two 

 dwarf eggs. 



Abnormal types of eggs have been reported also by Von Nathusius 

 (1895), F^re (1897 and 1898 b), Herrick (1899, a and b), Hargitt (1899 

 and 1912), Parker (1906), Patterson (1911), Glaser (1913), Curtis (1914b), 

 Chidester (1915), and Weimer (1918). Some of the abnormahties reported 

 might, of course, prove to be inherited, especially such as the double 

 yolks found by Glaser (1913); however, since this pubhcation is concerned 

 with normal eggs, further discussion of rare monstrosities may be omitted. 



The coloration of the shells of eggs has long been a subject of interest 

 to oQlogists. According to Newton (1893-96), older birds usually lay 

 darker-shell eggs. Newton says that some of the color is applied to the 



3 Variation and differentiation in Ceratophyllum. By Raymond Pearf, Olive M. Pepper, and Florence J. 

 Hagle. Carnegie Inst. Pub. no. 58 : 1-136. 1907. 



