8,2 MAINE AGRICUI.TURAL EXPERIMENT STATION. I909. 



respect to egg production for a less closely selected group of 

 mothers. Also the question as to whether there does not exist 

 in regard to egg production something corresponding to inherit-, 

 ance in "pure lines" as found by Johannsen in plants. It is 

 possible that this might be the case, without any sensible corre- 

 lation between mother and daughter appearing in the mass. 

 Further the influence of the male in transmitting fecundity to 

 his daughters needs to be carefully studied. All these prob- 

 lems, and others which they suggest are now under investigation 

 in this laboratory. Individual pedigrees are being kept for all 

 laying birds. Not only is the performance in respect to egg 

 production of each individual female tested by trap nests, but 

 the relative ability of each individual both male and female, to 

 transmit to their progeny a given degree of fecundity is being 

 thoroughly tested and measured. 



In comparing the results of the present study with previous 

 investigations in this field it must be kept in mind that we are 

 here dealing with fecundity sensu strictu. The earlier work 

 regarding the inheritance of reproductive capacity has, in all 

 cases known to the authors, had to do with fertility instead of 

 fecundity, using these terms as defined in this paper. Pearson * 

 has shown that there is a positive correlation between parent 

 and offspring in respect to fertility in man and in thoroughbred 

 race horses. Rommel and Phillips ** have shown that a similar 

 ■correlation exists between mother and offspring in respect to 

 •size of litter in brood sows. Pearson *** studying the records 

 of Weldon's mice breeding experiments was unable to demon- 

 strate a sensible parental correlation in respect to size of litter 

 in mice. The only direct positive experimental evidence which 

 has come to our attention showing that fertility in a mammal 

 can be increased by selective breeding is given by Marshall * for 



* Loc. cit. 



t Rommel, G. M. and Phillips, E. F. Inheritance in the Female Line 

 of Size of Litter in Poland China Sows. Proc. Amer. Phil. Soc, Vol. 

 XLV, pp. 245-254, 1907. Also in abstract; Biometrika, Vol. V, pp. 

 203-205. 1907. 



t On Heredity in Mice from the Records of the late W. F. R. Weldon. 

 Part I. On the Inheritance of the Sex-ratio and of the Size of Litter. 

 Biometrika, Vol. V, pp. 436-449, 1907. 



** Marshall, F. H. A. Fertility in Scottish Sheep. Trans. Highland 

 and Agr. Soc. of Scotland. 1908. Pp. (of reprint) 1-13. 



