20 AGRICULTURE OF MAINE. 



(2) The carrying out of definite and controlled matings, 

 both within the pure breeds and in crosses of high, and low pro- 

 ducing breeds, in order to discover whether this character milk 

 production is inherited in a similar way to the character egg 

 production, which has been studied in fowls. 



It is of course obvious that experimental work in this line 

 will take a considerable number of years to produce results. 

 The dairy cow is a slow growing animal and the character 

 milk production is one which does not come into expression un- 

 til full adult life is reached. However, the milk records now in 

 existence will make it possible to make some beginning at once 

 on an analysis of the inheritance of this character before the 

 results of experimental investigation come into hand. 



Collateral lines of investigation in connection with the cattle 

 breeding project include the study of sex determination, of 

 irbreeding and other topics. 



Influencing the Sex Ratio in Cattle. 



To control the sex of offspring is a thing which the breeder 

 of live stock would very much like to be able to do. Sex con- 

 trol, however, can never be hoped for until the laws of sex 

 determination are known. The search for these laws has en- 

 gaged the attention of students for centuries past. Many theo- 

 ries regarding the m.atter have been propounded, but only with- 

 in comparatively recent years have careful experimental and 

 statistical investigations on sex-determination been made. 



Some years ago the Maine Agricultural Experiment Station 

 undertook the collection of statistics in regard to cattle breed- 

 ing operations in order to find out whether the time of service 

 in relation to the period of heat had any relation to the sex of 

 the resulting calf. About i860 it was suggested by a Euro- 

 pean investigator named Thury that if cows were served at the 

 very beginning of heat there would be a tendency towards a 

 preponderance of heifer calves in the resulting offspring. On 

 the other hand if the cows were served relatively late in heat 

 there would tend to be more male calves born. Thury producefl 

 practically no concrete evidence in support of his theory and 

 after a few experimental tests of it on a small scale the mat- 

 ter dropped out of notice and has been practically forgotten. 

 Within the last few years, however, experimental studies on 



