inheritance; op fecundity in domestic fowl. 383 



tion are kept separate throughout, and that the vakie of the 

 former is not lessened if the latter is later found to be com- 

 pletely invalid, or in need of modification. It is carcely neces- 

 sary to say that the Mendelian hypothesis here presented is the 

 only simple one which the writer has been able to discover, after 

 over two years of study directed (whenever the time was availa- 

 ble) towards this particular end, which is capable of account- 

 ing satisfactorily for all the facts. Very many other Mendelian 

 schemes for the inheritance of fecundity have been tested 

 against the facts in the course of the work and discarded, one 

 by one, because inadequate. Of course, it still remains quite 

 possible, though perhaps not very probable, that there may be 

 an even simpler hypothesis which will equally well or better ac- 

 count for the facts. If so, by all means let us have it. But in 

 the meantime, it may be fairly be said, that the hypothesis here 

 presented brings together under a few, symbolically simple, gen- 

 eral statements a wide range of very diverse and complex facts 

 of inheritance. 



The strongest general evidence that the Mendelian hypothesis 

 here presented is at least a close approximation to the truth in 

 respect to the inheritance of a fecimdity in the fowl is found in 

 the fact that it accounts equally well for so wide a range of 

 diverse phenomena. In the two 'pure' parent races, one of 

 generally high and the other of generally low fecundity; the 

 two reciprocal crosses; and the twelve different kinds of mat- 

 ings in F2, we have a series of really independent iTieasures 

 of the validity of the hypothesis. It accords with the facts in 

 all but one (the niatings of C.I.G. $ 578 with Barred Fi ? 5 ) 

 of all of the different types of matings tested. The one excep- 

 tion probably has a physiological explanation (pp 373-377). In 

 view of these facts the cumulative probability that the hypothe- 

 sis applied represents at least a reasonable approximation to the 

 true interpretation of the results becomes very great, 



A possible criticism of the whole method of this investigation 

 might be found in reference to the measure of fecundity which 

 has been used throughout, namely, the winter &gg production. 

 Regarding this matter it should be said that the very reason why 

 winter egg production was adopted as the unit of measure in 

 all of the fecundity work of this laboratory was because a thor- 



