DWARF EGGS OF DOMESTIC FOWL. 325 



vented the yolk from entering the duct but did not otherwise 

 disturb the mechanism, did not produce dwarf eggs. Some 

 stimulus other than the condition of the sex organs is necessary 

 to start the secreting activity of the duct. In normal eggs or 

 in dwarf eggs with yolk this stimulus (mechanical or chemical) 

 is furnished by the yolk. 



The fact that all dwarf eggs without yolks contain some 

 nucleus firmer than normal albumen, together with the fact 

 that in one case where the bird had a dwarf egg with such a 

 nucleus in the shell gland at autopsy no yolk was found in the 

 body cavity suggests that when the ovary is maturing and 

 ovulating successive yolks a mechanical stimulus may initiate 

 the secretion of the egg envelopes. 



The results of surgical experimentation show conclusively that 

 in a certain stage of activity the oviduct responds to a mechani- 

 cal stimulus by the secretion of the egg envelopes. 



Various facts indicate that the functional condition of the 

 oviduct depends upon some substance formed in the ovary 

 usually at the time yolks are maturing but in certain patho- 

 logical cases at other times also. This substance is probably 

 an internal secretion carried by the blood since the ovary can 

 cause the enlargement to functional size of a small piece of 

 oviduct, the normal nervous connections of which have been 

 destroyed. The fact that dwarf eggs are produced only when 

 the bird is maturing and ovulating yolks and the fact that 

 more than 50 per cent, of the trials to induce egg formation 

 around artificial yolks were failures, suggest that the sex 

 organs must be and must remain in absolute functional condi- 

 tion until the egg is completed. 



Summary. 



1. An occasional individual of any breed of domestic fowls 

 produces one or more small abnormal eggs. These eggs mav 

 be called dwarf eggs. 



2. There are two distinct shape types of dwarf eggs: first, 

 the prolate spheroidal or egg shaped type, and second, the 

 cylindrical type. The prolate spheroidal shape is more com- 

 mon. In fact 95.4 per cent, of the dwarf eggs studied were of 

 this type. 



