99 8 



Journal of Agricultural Research 



Vol. VI, No. 25 



Table XXI gives the differences between various of these correlation 

 coefficients, the probable error of the differences, and the ratio of each 

 difference to its probable error. 



Table XXI. — Deviation in correlation coefficients, the probable error of the differences 

 and the ratio of each difference to its probable error 



Class of eggs. 



Free-yolked dwarf. 



Do 



Do 



Yolkless dwarf 



Do 



Do 



Small-yolked dwarf 



Do 



Do 



Normal 



Do 



Do 



Pairs of characters, the correlation coefficients of 

 which are compared. 



Breadth with weight — length with weight 

 Length with weight — length with breadth 

 Length with breadth — index with weight . 

 Breadth with weight — length with weight 

 Length with weight — length with breadth 

 Length with breadth— index with weight . 

 Breadth with weight — length with weight 

 Length with weight — length with breadth 

 Length with breadth — index with weight. 

 Breadth with weight — length with weight 

 Length with weight — length with breadth 

 Length with breadth — index with weight. 



Difference in 



correlation 



coefficients 



with probable 



error. 



.01 7 ±0.009 



.059± .015 

 . 466 ± .050 



• oo5± 016 

 . 080 ± .024 



• 476± .067 

 .043± .049 

 .o8i± .068 



• 667± .142 

 . 256 ± .023 



• 49°± .038 



• ooi± .045 



Differ- 

 ence 



probable 

 error of 

 differ- 



2.0 

 3-9 



Pairs of characters cor- 

 related. 



Classes compared. 



Difference in 



correlation 



coefficients 



with probable 



error. 



Differ- 

 ence 



probable 

 error of 

 differ- 

 ence. 



Length with breadth. . . 



Do 



Do 



Length with weight 



Do 



Do 



Breadth with weight. . . 



Do 



Do 



Index with weight 



Do 



Do 



Yolk weight with egg 



weight. 

 Yolk weight with albu- 

 men weight. 



Free-yolked — yolkless . 

 Yolkless — small-yolked 

 Small-yolked — normal . 

 Free-yolked — yolkless . 

 Yolkless — small-yolked 

 Small-yolked — normal . 

 Free-yolked — yolkless . 

 Yolkless — small-yolked 

 Small-yolked — normal . 

 Free-yolked— yolkless . 

 Yolkless— small-yolked 

 Small-yolked — normal . 

 do 



do 



0.030 ±0.02 5 

 . 085 ± . 060 

 •675± 

 .oo9± 

 .o8 4 ± 



• 26o± 



• 03i± 



• o 3 6± 

 •047± 



• 040± 

 .2761b 



• oo7± 

 .122 



.223 



1.2 

 1.4 

 IO-4 

 •7 

 2. 1 

 5-9 

 2.4 

 1.2 

 1-5 

 2-S 



From Table XX the following points may be noted : 



1. In each class of dwarf eggs the correlation between the two dimen- 

 sions is positive and is certainly significant — that is, a broad dwarf egg 

 is also long, and vice versa. The shape of the egg is no doubt determined 

 by the action of the longitudinal and circular muscle fibers of the oviduct 

 walls, especially during the formation of the egg membrane and shell. 

 The egg is a fluid body which tends to take a spherical shape when not 

 under pressure. At the time an egg receives its membrane and shell 

 a normal egg or almost any dwarf egg is larger than the normal diameter 

 of the oviduct. It is therefore under pressure which tends to elongate 

 it in the direction of the long axis of the duct. The degree of pressure 

 and, hence, the resulting degree of elongation will depend on (a) the size 

 of the egg compared to the diameter of a cross section of the duct, and 



