THREE CALVES AT A TIME 
After bearing a single calf three times in succession, the Holstein-Friesian cow here shown 
suddenly bore triplets. 
to what extent heredity is responsible for this multiple birth. 
known that heredity is one of the causes of such births. 
As little is known of her ancestry, it has been impossible to find 
From other studies, it is 
If a thorough investigation of 
many cases like this were made, ways might be found for getting a strain that would 
regularly produce at least two calves at a time, instead of one. 
tendency is inherited, for the results are 
irregular. W. Weinberg, whose study 
dealt with large numbers of cases, 
decided‘ that in man the tendency to- 
ward multiple births is inherited in 
Mendelian fashion, apparently behaving 
as a recessive; but the results did not 
altogether bear out this simple state- 
ment, and he concluded that although 
heredity was at the bottom of it, external 
factors also played an important part. 
No single external factor was as im- 
portant as heredity, he thought, but 
the sum total of external factors was 
probably more important than heredity. 
(Fig. 15.) 
Weinberg’s methods of investigation, 
being statistical, were hardly sufficient 
to decide this point, and all that can 
be said at present is that heredity is at 
least an important factor in the produc- 
tion of plural births. 
Few attempts to increase the fecun- 
dity of a strain by selecting the animals 
which produce an unusual number of 
young, are on record. To a certain 
degree, of course, such selection is 
always going on, half unconsciously, for 
animals which are poor breeders are 
discarded, while those which are good 
breeders are valued highly and bred 
4 Archiv fur Rassen- und Gesellschafts-Biologie, Band 6, pp. 339, 470, 609, 1909. 
136 
