154 MAINE AGRICULTURAL LXPERIMI^NT STATION. I909. 



extending over six generations has investigated the effects 

 resulting from feeding fowls a purely meat diet. He notes 

 among other results an impairment of general constitutional 

 vigor amongst his birds in the later generations, and also a 

 greatly reduced hatching quality of the eggs. 



The present study has shown that high winter egg production 

 has, on the average, an adverse effect on the hatching quality 

 of the eggs produced by the same birds in the subsequent hatch- 

 ing season. This again can probably be regarded as the result 

 of a reduction of constitutional vigor following heavy laying. 

 Continued heavy egg production involves great metabolic activ- 

 ity on the birds' part in the transformation of matter and 

 energy and must fatigue the organism. It is not surprising 

 that under such circumstances the developmental machines 

 (fertilized eggs) produced are not absolutely perfect. The 

 finding of a negative correlation between fecundity and hatch- 

 ing quality (= germinal viability or vigor) is of some general 

 theoretical interest. There is considerable reason to believe 

 that a similar condition of affairs exists in man. High fecun- 

 dity and high infant mortality (and probably also prenatal mor- 

 tality) are very generally associated. And are not the causes 

 probably very similar in the two cases? In those social classes 

 showing the greatest fecundity, there exist, speaking broadly, 

 bad conditions of housing and nutrition all tending along with 

 the organic fatigue incident to the high fecundity itself, to 

 reduce the general vital condition or constitutional vigor, and 

 with it the viability of the developing germ and growing 

 organism. 



Similarly adverse housing conditions most probabl}' produce 

 the l>ad eft'ect which the}' have been shown (by Dryden, Stewart 

 and -Vtwood. and others, as well as in the ])resent ])apcr ) to 

 have upon hatching quality by lowering the general vital con- 

 dition of the fowls. 



To this factor of constitutional vigor as affecting hatching 

 quality of eggs the data of the present paper add another, viz., 

 inheritance. Hatching quality of eggs is in some measure a 

 "bred in the bone" character of poultry, and must be reckoned 

 with as such. The existence of this factor manifests itself in 

 two ways in our results: one by the persistence of relatively 

 the same degree of hatching quality in the same bird in succes- 



