Vol. XXIV. March, 1913. No. 



BIOLOGICAL BULLETIN 



DATA ON SEX DETERMINATION IN CATTLE.' 



RAYMOND PEARL AND H. M. PARSHLEV. 



INTRODUCTION. 



In a paper from this Station published over twenty-two years 

 ago Russell 2 presented certain statistics which he collected regard- 

 ing the relation between the sex of a calf and the time in the 

 period of heat (oestrus) at w r hich the copulation occurred which 

 gave rise to it. Data were collected in regard to (a) whether 

 service occurred early in the "heat," or in the middle of the period 

 of oestrus, or late in the "heat"; and (6) the sex of the resulting 

 offspring. In the published results only the data for "early" 

 and "late" coitus were presented. The figures given were as 

 follows (loc. cit., p. 209): 



"82 cows served during the first part of heat produced 31 

 bull calves and 51 heifer calves. 



"76 cows served during the last part of heat produced 42 

 bull calves and 34 heifer calves." 



These figures were admittedly meager. After the paper re- 

 ferred to was published Dr. Russell continued the collection of 

 statistics on this subject but published nothing further. Upon 

 resigning from the Station staff he very kindly turned over to 

 the senior author of the present paper all his original schedules. 

 The complete collection of statistics has recently been subjected 

 to analysis with the results set forth in this paper. 



The original schedules contain spaces for the recording of the 

 following information: (i) Breed and age of bull. (2) Breed of 



1 Papers from the Biological Laboratory of the Maine Agricultural Experiment 

 Station, No. 42. 



2 Russell, F. L., "Breeding Statistics," Maine Agr. Expt. Stat., Ann. Rept. for 

 1891, pp. 208, 209. 



205 



