420 



is thus no evidence of an inheritance of the tendancy to lay multiple 

 yolked eggs in the family as in the case noted by Panum?-. He describes 

 an instance where four daughters of an old hen known to lay double- 

 yolked eggs, themselves produced such eggs. Such a case does not, of 

 course, prove an inheritance of this tendency. Experience in this 

 laboratory where detailed records of large numbers of birds are kept 

 shows that any individual is liable to produce at sometime in her laying 

 career an abnormal egg. If mother and daughter both chance to do this 

 in one or two isolated instances, it is no proof of inheritance. 



External Characteristics and Size of the Egg. 

 The triple-yolked egg though large in size was of normal shape, 

 being more pointed at one end than the other. This is clearly shown 

 in Fig. 1. Its shell was firm and hard. It had the surface texture and 

 smoothness which is normal. The shell was of the delicate brown color 

 which is normal for the egg of the Barred Plymouth Rock. The dimen- 

 sions of the egg were as follows: 



Length 70,7 mm 

 Breadth 64,2 - 

 Weight 87,10 g*. 

 For the normal Barred Plymouth Rock egg with a single yolk the 

 average dimensions, obtained from the unpublished data collected in 

 this laboratory, are as follows: 



Mean length (normal egg) = 56,32 mm 

 - breadth - - = 41,92 - 



weight - - = 55,26 g. 



From these figures it is apparant that the egg with three yolks is 

 much larger than the normal single yolked egg. In this respect the 

 present specimen differs from those described by Valenciennes. He says 

 with regard to this point in his cases (loc. cit. p. 3): "Leur grosseur 

 était celle des œufs ordinaires". It is a well known fact that double 

 yolked eggs may be little or no larger than normal single yolked eggs^. 

 Yet common observation indicates clearly enough that the great majority 

 of such eggs are larger than the normal. It seems remarkable that 



3 Panum. P. L., Untersuchungen über Entstehung der Mißbildungen. Berlin 

 1860. 



4 This weight is calculated, as unfortunately the egg was not weighed. The 

 value given was determined by first calculating the volume of the egg on the as- 

 sumption that it was an oblate spheroid, and then multiplying the volume so obtained 

 by the mean specific gravity. This method has been proved, in unpublished in- 

 A'estigations carried out in this laboratory, to give very accurate results. 



5 Immermann, F., Über Doppeleier beim Huhn. Inaug. -Diss. Basel. 1899. 

 S. 8 u. 9. 



