Sept. 18, 1916 Dwarf Eggs 102 1 



decided, since they did not contain a trace of yolk. The continued 

 occurrence of nesting records and the condition of the ovary at autopsy 

 show that the reproductive cycles of the ovary were not interrupted. 

 The dwarf eggs occurred during such a cycle. 



The five cases of dwarf-egg producers cited above have several things 

 in common: (1) Each bird was a normal, high-laying individual which 

 became unable to produce normal eggs on account of a pathological 

 condition of the oviduct. (2) In every case the part of the duct affected 

 was the posterior end of the funnel, or the anterior end of the albumen- 

 secreting region, or both. (3) The disturbance in each case was of a 

 nature to constrict or prevent the normal expansion of the lumen of the 

 duct. (4) In no case was the passage completely closed. (5) In each 

 case there was convincing evidence that the ovary was in a normal repro- 

 ductive cycle at the time the dwarf egg was produced. 



Five of the sixteen 1 dwarf eggs produced by these birds contained as 

 a nucleus a small quantity of yolk not inclosed in a vitelline membrane. 

 This yolk was no doubt a part of a normal yolk, the rest of which was 

 absorbed by the visceral peritoneum. Three of the five birds were 

 absorbing yolk in this manner at the time of autopsy. The presence 

 of a part of a yolk in the egg may have been due to any one of several 

 causes. The three which seem most probable are the following: 



1 . A yolk may have been broken during its passage into the duct and 

 only a part of it may have entered the duct. 



2. A part of a yolk ovulated into the body cavity and, broken either 

 before or after ovulation, may have been picked up by the funnel. 



3. A normal yolk may have entered the duct and being unable to pass 

 the pathological portion may have been broken and a part of it extruded 

 into the body cavity. The remaining portion may have passed the 

 obstruction, becoming the effective stimulus for the formation of the egg 

 envelopes. 



The effective stimulus in the case of the dwarf eggs which do not contain 

 any yolk is difficult to ascertain. Some of these eggs contained what were 

 apparently normal chalazae. Most of them contained coagulated fibers 

 which resembled the fibers of which chalazae are formed. It is possible 

 that in some or all of these cases a normal yolk has entered the duct, 

 stimulated the upper duct to secrete chalazae and some albumen, passed 

 as far as the obstruction, and then been extruded, leaving behind sufficient 

 chalazal material and albumen to furnish the mechanical stimulus neces- 

 sary for the completion of the egg. Some of these eggs contained lumps 

 of hardened albumen which may have arisen from albumen left in the 

 duct or abnormally secreted. When the ovary is in a particular condi- 

 tion, such a mechanical stimulus may cause the secretion of the egg 

 envelopes. It must be kept in mind, however, that a dwarf egg did not 



1 In two other cases the presence or absence of yolk was not recorded. 



