sept, is, 1916 Divarf Eggs 989 



the nucleus of coagulated fibers of albumen was drawn out in a line 

 parallel to the long axis of the egg. Further, at one of our routine 

 autopsies there was found in an oviduct a string of albumen 5 or 6 cm. 

 long and not more than 1 cm. in diameter. This was wrapped around a 

 long thread of coagulated albumen fibers which lay parallel to the length 

 of the duct. It seems probable that the form of the stimulating nucleus 

 is one of the factors in determining the shape of the egg. When the 

 stimulus is small in amount and drawn out, the degree of stimulation 

 must be small but the area covered large. 



In the prolate-spheroidal eggs the nucleus is usually of globular form — 

 that is, its shape is comparable to the shape of a normal yolk. All the 

 eggs with small-formed yolks were of the prolate-spheroidal type. It has 

 been noted that indices for dwarf eggs with small yolks are higher than 

 those for normal eggs and lower than those for other prolate-spheroidal 

 eggs. The order for the value of index is thus the reverse of the order for 

 the size characters. Later it will be shown that within each group of 

 dwarf eggs the index is negatively correlated with weight. In earlier 

 investigations (3, 5) it has been shown, first, that the indices for multiple- 

 yolked eggs lie below the range of variation for the indices of normal 

 eggs, and, second, that within the normal eggs of an individual the index 

 is negatively correlated with weight. The results from the study of 

 dwarf eggs, therefore, extend the former evidence that the smaller the 

 egg the broader it is in proportion to its length. Two factors may be 

 working together to produce this negative correlation between index and 

 weight. First, the greater the long diameter of the nucleus — be it yolk 

 drop, normal yolk, or two or three yolks in tandem — the longer will be the 

 area of oviduct stimulated at the same time; and, second, when a plastic 

 body is forced (by peristalsis) through an elastic tube the tube will offer 

 less mechanical resistance to the passage of a small than a large body. 

 This mechanical factor is probably of great importance in determining 

 the shape of the egg. 



C. — RELATIVE VARIABILITY OF DWARF AND NORMAL EGGS 



Tables IV and V give also the data for comparing the variability of the 

 different classes of prolate-spheroidal dwarf eggs with each other and with 

 normal eggs. Table IV gives for normal eggs and for each class of egg- 

 shaped dwarf eggs the standard deviation for length, breadth, index, and 

 weight, and the coefficient of variation for each of these characters except 

 index. 1 In the case Of normal eggs and dwarf eggs with formed yolks it 

 also gives the variation constants for each egg part (yolk, albumen, and 

 shell). A comparison either of standard deviations or of coefficients of 

 variation shows that normal eggs are less variable in each character meas- 

 ured than are the eggs of any class of prolate-spheroidal dwarf eggs. The 



1 Coefficients of variation of percentage characters have no physical significance. 



