CHAPTER XXXIX 
CONCLUDING REMARKS 
Although we have discussed a deal of material in this account of 
genetics in relation to animal breeding, it must be apparent to any student 
that we are still woefully lacking in detailed and precise knowledge. 
In fact, as yet we seldom have accurate information with respect to the 
most simple and easily determined matters, such as growth curves in the 
various breeds and races of livestock, comparative production curves, 
and the like, the obtaining of which is largely a matter of routine. 
Such data are not even genetic data, strictly, but they are so necessary 
for the application of genetics to animal breeding that genetics proper 
must almost mark time until they can be obtained. The necessity of 
having accurate standards of judgment obviously need not be debated 
before an intelligent audience. 
> Our dearth of detailed knowledge is particularly noticeable, however, 
in the field of genetics proper. It has been said—and there is much 
justification for the statement—that our knowledge of heredity is not 
secure with respect to any character until it has been found possible to 
analyze it and determine the factors which enter into it. If such a cri- 
terion then be applied to our knowledge of heredity in horses and cattle, 
for example, we have little cause to congratulate ourselves upon the 
extent of our accurate knowledge; for in either of these animals the 
number of factors accurately known could be counted on the fingers of 
both hands. It is a far call from such a state of affairs to that obtaining 
in Drosophila ampelophila in which knowledge has been derived concerning 
about 150 factors, many of which have been arranged in a systematic, 
coordinated scheme. Our knowledge is very meagre especially with 
respect to those factors which affect primarily economic characters in 
domestic animals, such as milk production in dairy cows, fertility, vigor, 
and like characters or character-complexes. Here we have a very good 
beginning in Pearl’s analysis of winter egg production in domestic 
fowls; but compared with the amount of information yet to be gained 
we see how long is yet the road to be travelled. But this beginning which 
Pearl has given us is very encouraging ; it leads us to feel confident that 
our knowledge of accurate details of heredity will be pushed further and 
further. 
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