Sept. 18, 1916 



Dwarf Eggs 



979 



of the bird laying the dwarf egg is available. Furthermore, autopsies 

 were made on several of these birds, and the condition of their sex organs 

 was observed. 



I.— CLASSIFICATION OF DIFFERENT TYPES OF DWARF EGGS, FIRST, 

 IN RESPECT TO SHAPE, AND SECOND, IN RESPECT TO PRESENCE 

 OR ABSENCE OF YOLK 



The dwarf eggs of the fowl vary greatly in size and shape. Plate CXII 

 shows 14 of these eggs with a normal egg laid by a 9-months-old pullet 

 for comparison. From this illustration it may be seen that there are two 

 distinct types of dwarf eggs in respect to their shape: The prolate- 

 spheroidal type, similar in shape to a normal egg; and the cylindrical 

 type, which is much longer in proportion to the breadth. The cylin- 

 drical eggs are shown in the first row of Plate CXII. These cylindrical 

 eggs occur much less frequently than do the dwarf eggs of the prolate- 

 spheroida.1 type. Of the 261 dwarf eggs on which complete data are 

 available only 12, or 4.6 per cent, were of this form. 



Not only do the dwarf eggs differ in respect to size and shape but 

 there is a difference in internalstructure. These dwarf eggs are some- 

 times defined as yolkless eggs, or small eggs containing a small quantity 

 of yolk usually not in a yolk membrane. During this investigation the 

 contents of 274 dwarf eggs were examined. It was found that some of 

 these eggs contained no yolk but appeared to be formed around a nucleus 

 which consisted of a few strings of coagulated albumen, apparently 

 untwisted chalazal threads and also sometimes small lumps of hardened 

 albumen or small blood clots. On the other hand, some contain small 

 yolks in yolk membranes. These yolks do not usually have visible germ 

 disks. The weight of these yolks varies from 1 gm. to nearly 8 gm. 

 More than half of all the eggs opened, however, contained some yolk 

 which was not inclosed in a yolk membrane. Dwarf eggs may then be 

 classified according to the nonoccurrence of yolk and the condition of the 

 yolk when present as, first, yolkless, second, with some yolk not in a 

 membrane, and third, with one small yolk. In Table I the dwarf eggs 

 are classified both according to form and yolk content. 



Table I. — Classification of dwarf eggs both as to shape and as to yolk content 



a Dimensions not recorded. 



