8 MAINE AGRICULTURAL EXPERIMENT STATION. 



The two yolks of a double-yolked egg may enter the oviduct 

 simultaneously and pass the entire length of the duct together 

 receiving from the duct an entire common set of egg envelopes, 

 or they may come together at any level of the oviduct from the 

 funnel mouth to the beginning of the isthmus. It is highly 

 probable that the two ovulations may be either simultaneous or 

 that they may be separated by any period up to the normal 

 period between ovulations. 



The production of a double-yolked egg is evidently seldom 

 caused by the simultaneous discharge of two normal separate 

 follicles into the oviduct. Usually it is caused by the successive 

 discharge of separate follicles at times varying from simul- 

 taneity to the normal period, and by the subsequent union of 

 the eggs in the duct due to a difference in the rate of passage 

 of the successive eggs. 



PiL\CTicAL Hints on Breeding for Egg Production. 



For many years there has been in progress at the Station an 

 investigation of the laws of inheritance of egg producing abilit}- 

 in poultry. The following suggestions, compiled from Bulletin 

 231 of this Station, are offered as a basis for the improvement 

 of poultry in egg production by breeding. 



I. Selection of all breeding birds first on the basis of co}i- 

 stitiitional vigor and vitality making the judgment of this so far 

 objective as possible. In particular the scales should be called 

 on to furnish evidence, (aj Do not use as a breeder a cockerel 

 which (in the case of Plymouth Rocks or Rhode Island Reds 

 or Wyandottes) has not attained a weight of at least eight 

 pounds at ten months of age, and better, nine pounds. Use 

 no pullet as a breeder which does not weigh at least five and 

 one-half pounds at the same age. (bj Let all deaths in shell, 

 and chick mortality, be charged againsl the dam, and only 

 those females used as breeders a second time which show a 

 high record of performance in respect to the vitality of their 

 chicks, whether in the egg or out of it. This constitutes one 

 of the most valuable measures of • constitutional vigor and 

 vitality which we have. If for no other reason than to measure 

 this breeding performance, a portion of the breeding females 

 each year should be pullets. In this way one can in time 

 build up an elite stock with reference to hatching quality of 

 eggs and vitality of chicks, (c) Let no bird be used as a 



