1032 



Journal of Agricultural Research 



Vol. VI, No. 2S 



Table XXX gives the number and percentage of each kind of dwarf 

 eggs classified as to the nature of the contained nucleus. 



Table XXX. — Dwarf eggs classified according to the nature of the contained nucleus 



From Table XXX we see 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 for birds killed while a dwarf egg was in 

 the duct or immediately after one was laid, indicates that in at least 

 55 per cent of the cases 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 case 27, discussed on page 1027, the 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 in the shell gland 

 and 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 case it is impossible to tell whether the yolk was broken during or 

 after ovulation. It is possible either that the yolk was ovulated into 

 the body cavity and subsequently 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. 



Parker (10) described an ovum in ovo where the inclosed egg was 

 yolkless and the inclosing egg contained a little "yolk substance." He 

 believed that this "yolk substance" was the remnant of a normal yolk 

 which had been ruptured and most of which had escaped. This sug- 

 gested to him the question, "Is it possible that the yolkless condition of 

 the inclosed egg is also due to the loss of its yolk ? " However, he believes 

 the evidence convincing "that albumen can be formed by the oviduct 

 without the presence of yolk." 



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 production only quantitatively — that is, in the size of the stimulating 

 yolk. 



