122 MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



Specifically the possibilities here are large. There are many 

 sorts of things by which a hen's laying may be disturbed and 

 reduced. The action of such environmental circumstances fur- 

 thermore cannot be prevented nor their disturbing influence 

 upon a selection experiment eliminated by "keeping the environ- 

 ment constant" during the course of the experiment. This, of 

 course, is the usual experimental method of attempting to safe- 

 guard against environmental factors disturbing the interpre- 

 tation of the results of an experiment having to do with in- 

 heritance. But, as a matter oi fact, leaving aside as of no real 

 importance in the present discussion the fact that with such 

 animials as poultry certainly it is physically impossible to obtain 

 anything more than average uniformity of environment during 

 a long period of years, there is a further point not to be lost 

 sight of. This is' that the effect of any adverse environmental 

 circumstance acting upon an animal during the course of a 

 long continued experiment in selection must tend to become 

 progressively cumulative as time goes on, if it he really efficient- 

 ly adverse at all. 



What is meant is this : Suppose at the outstart of the ex- 

 periment something in the method of feeding, or in the method 

 of incubation, or of rearing the chicks was of a character such 

 as to afifect adversely, even to a slight degree, the vitality or 

 constitution of the birds. Even without any true inheritance 

 of this effect nevertheless its action must necessarily tend to 

 become cumulative for purely physiological reasons, because 

 (to confine the discussion to the case in hand, namely the 

 domestic fowl) it admits of no question that a constitutionally 

 weak or debilitated fowl lays an egg which is "weak" also. The 

 elaboration of the yolk and of the albumen takes place within 

 the hen's body. These substances serve as the food of the 

 developing embryo. It is certain from observation of both 

 tgg and chick that the same kind or quality of food is not 

 furnished to the embryo by the &gg manufactured in the body 

 of a strong fowl as is furnished in an tgg manufactured in the 

 body of a weak fowl. This Is a fact which is well known to 

 everyone who has had experience in the hatching and rearing 

 of poultry. To analyze minutely all of the biological and chem- 

 ical factors involved would certainly be a very difficult, indeed 

 an almost impossible task, yet because such analysis is not easily 

 possible in no wise militates against the fact itself. 



