DWARF EGGS OF DOMESTIC FOWL. 319 



of normal eggs continuing as if the dwarf had been a normal 



egg- 



The autopsy records of normal birds which produce one or 

 occasionally two or three dwarf eggs at wide intervals show 

 that the sex organs are morphologically normal. In the cases 

 where autopsy immediately followed the production of the 

 dwarf egg the sex organs' were in full functional activity and 

 in every case but one the body cavity contained free yolk, 

 indicating that all or a part of a yolk had failed to enter or had 

 later been extruded from the duct. In one case the follicle had 

 failed to rupture completely and was draining yolk from the 

 torn yolk membrane. A part of this yolk was free in the body 

 cavity and a part was in the dwarf egg. 



C. EVIDENCE IN CASES WHERE A DWARF EGG FORMS A PART OF 

 A COMPOUND OR A DOUBLE EGG. 



i. Compound eggs of which one part is a dwarf .egg. 



Recently an abnormal egg was produced by a bird in the 

 Station flock which gives additional evidence as to physiologi- 

 cal conditions and nature of stimuli which may result in the 

 production of a dwarf egg. The shell of this egg is shown in 

 Figs. 57 and 58. This egg was a compound egg. The two 

 parts were of quite unequal size. The component which filled 

 the larger part of the shell contained a normal yolk in a normal 

 membrane but there was a slight tear in this membrane and 

 free yolk was protruding from this tear. The hole which faced 

 the small component egg was quite small and little of the yolk 

 had escaped. This part of the egg had normal chalazae and 

 thick and thin albumen. The other part which filled the smalt 

 portion of the shell contained a drop of free yolk surrounded 

 by a thick albumen envelope which was quite distinct from the 

 albumen of the large part of the egg. No thin albumen was 

 present in this part of the egg. An incomplete shell membrane 

 separated the two components. 



The fact that when an egg is entering the isthmus as much 

 and only as much of it as has passed in is covered with mem- 



