DWARF EGGS OF DOMESTIC FOWL. 



3 2 3 



Table 9. 



Dwarf Eggs Classified According to the Nature of the Con- 

 tained Nucleus. 



Nature of Nucleus. 



Number 

 dwarf eggs. 



Per cent, 

 dwarf eggs. 



Subtotals 

 or per 



rents. 



Drop of yolk, no yolk membrane 



141 

 10 



27 



96 



51.46 

 3.65 

 9.85 



35.04 



55 .11 



64.96 



Chalazal threads with or without lumps of 



100.00 



Total 



274 



100.00 





This table shows that in 9.85 per cent, of the dwarf eggs the 

 stimulus to the active duct was an abnormally small yolk which 

 for some unknown reason was produced and ovulated by the 

 ovary. These cases apparently differ from normal egg pro- 

 duction only quantitatively. That is, in the size of- the stimu- 

 lating yolk. 



From this table we see also that 55.11 per cent, of all the 

 dwarf eggs opened contained a portion of a yolk and 3.65 per 

 cent, contained a broken yolk membrane. This fact in connection 

 with the autopsy records already discussed (pp. 316-318) for 

 birds killed while a dwarf egg was in the duct or immediately 

 after one was laid, indicate that in at least 55 per cent, of all 

 the cases of dwarf egg production the immediate stimulus to 

 the active duct was a part of an egg yolk, the rest of which 

 was absorbed from the visceral peritoneum. In one case th.: 

 vitelline membrane of the yolk which furnished the stimulus 

 was still within its ovarian follicle although part of the yolk 

 was in the dwarf egg found in the shell gland and the most of 

 the rest in the body cavity. In this case the yolk was broken 

 during ovulation and only a part of it entered the duct. In the 

 other cases it is impossible to tell whether the yolk was broken 

 during or after ovulation. It is theoretically possible either 

 that the yolk was ovulated entire into the body cavity and sub- 

 sequently broken and a part taken up by the duct, or. on the 

 other hand, it may have entered the duct and later been broken 

 and a large part of it expelled. 



