292 MAINE AGRICULTURAL EXPERIMENT STATION. I915. 



being absorbed at a rapid rate. The occurrence of double eggs 

 shows that one egg did not always get out of the duct in time 

 to make way for the succeeding egg. The occurrence of the 

 Qgg composed of four concentric eggs suggests that the direc- 

 tion of the movements of the egg must have been considerably 

 disturbed so that this egg passed up and down the duct several 

 times before it was discharged into the body cavity. The con- 

 dition of the internal organs of the bird indicates that the 

 physiological processes of digestion, absorption and secretion 

 were not seriously disturbed. 



The forward end of the oviduct or egg tube arises very eaily 

 in the development of the chick embryo. The tube then grows 

 backward until it reaches the region of the vent. The most 

 probable explanation for the occurrence of the oviduct found 

 in the case described is that in early embryonic development 

 (probably on the sixth or seventh day of incubation) the back- 

 ward growth of the oviduct stopped permanently while the 

 differentiation of the part already formed continued in the 

 normal manner. 



As in other cases where the passage of the egg is prevented 

 the sex organs passed through their normal reproductive cycle.; ; 

 the oviduct functioned as far as the point where the passage 

 was interrupted ; the eggs were then returned to the body 

 cavity and resorbed. The number of eggs and empty egg mem- 

 branes found in this fowl which was apparently in a perfectly 

 normal physical condition show that a bird may possess very 

 great power of resorption of its own eggs. 



ON THE REFRACTIVE INDEX OF THE SERUM IN A 

 GUINEA-CHICKEN HYBRID.* 



This is a record of certain results regarding the refractive 

 index of the blood serum of a genus-hybrid produced from 

 the mating Cornish Indian Game $ X Guinea Fowl 9 . 



Our results show that (i) there is a definite, characteristic. 

 and permanent difference between the refractive index of the 

 serum of the fowl and that of the guinea; and (2) that in the 

 h)-brid the guinea parent is dominant in respect of the physico- 



*This is an abstract of a paper by Raymond Pearl and John W. 

 Gowen, having the same title and published in Proceedings of the So • 

 ciety for Exper. Biology and Medicine. Vol. XII, p. 48, 1915. 



