THE INHERITANCE OF FECUNDITY 365 



During the course of this investigation into the inheritance of 

 fecundity in the domestic fowl, which has now involved thirteen genera- 

 tions and several thousand individuals, two definite and clear-cut 

 results have come to light. These are : 



First : that the record of egg production or fecundity of a hen is not, 

 of itself, a criterion of any value whatsoever from which to predict the 

 probable egg production of her female progeny. An analysis of the 

 records of production of large numbers of birds shows beyond any pos- 

 sibility of doubt that, in general, there is no correlation between the 

 egg production of individuals and either their ancestors or their 

 progeny. 



Second: that, notwithstanding the fact just mentioned, fecundity 

 is, in some manner or other, inherited in the domestic fowl. This 

 must clearly be so, to mention but a single reason, because it has been 

 possible to isolate and propagate from a mixed flock "pedigree lines" 

 or strains of birds which breed true, generation after generation, to 

 definite degrees of fecundity. Some of these lines breed true to a high 

 condition or degree of the character fecundity; others to a low state or 

 degree. 



Definite as these results are, they give no clue as to how fecundity is 

 inherited; what the mechanism is. It is believed that now a first ap- 

 proximation to the solution of this problem has finally been reached. 

 While there remain obscure points yet to be cleared up, and more data 

 are needed definitely to decide between certain alternatives, yet the 

 results now in hand appear to indicate quite clearly the general charac- 

 ter of the mechanism of the inheritance of fecundity, and to show what 

 lines further investigation of the problem may most profitably take. 



At the outstart it will be well to understand clearly what is meant 

 by the term fecundity as here used. I have used the term " fecundity " 

 only to designate the innate potential reproductive capacity of the indi- 

 vidual organism, as denoted by its ability to form and separate from 

 the body mature germ cells. Fecundity in the female will depend upon 

 the production of ova and in the male upon the production of sper- 

 matozoa. 



Fecundity is obviously a character depending upon the interaction 

 of several factors. In the first place the number of ova separated from 

 the body by a hen or any other animal must depend, in part at least, 

 upon an anatomical basis, namely the number of ova present in the 

 ovary and available for discharge. Further there must be involved a 

 series of physiological factors. It has been possible to prove that the 

 mere presence of an anatomically normal reproductive system, includ- 

 ing a normal ovary with a full complement of ova, and a normal ovi- 



eomplete report with full presentation of the experimental data will shortly 

 be published in the Journal of Experimental Zoology. 



