332 Bulletin 162. 



Avg. 280 



It will be seen that the larger number of cows fall into the 

 second group, i. e., those whose period of gestation is uniform 

 with a single exception. Taking group A and group B together, 

 it w^ould seem that in the great majority of cases after a cow has 

 had one or two calves it ought to be possible to predicate her 

 period of gestation quite closely. It has already been shown that 

 the gestations where twins have been carried, average quite a 

 good deal shorter than when but one calf is born. This is true 

 not only of our own observations but of Karl Spencer's as well. 

 The difference is still more marked if the twin gestations are com- 

 pared wdth the other gestations of the same animal as is shown in 

 detail below. 



Table III. 



Avg. 282 



