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always from strong and usually mature males. On the other hand, the females of 
a herd are all preserved. If Ave deem that vigor, strength, and similar constitu- 
tional characters are transmitted, and that these can be intensified or accumulated 
in succeeding generations, it is not unreasonable to suppose that males may have 
acquired by natural selection alone an ability to transmit their characters more 
strongly than the females. The only way of throwing light upon this question is by 
careful observation through many generations and by reciprocal crosses, which will 
eliminate the error which might arise from differences in prepotency due to pure 
breeding. 
One of the most remarkable series of experiments of recent times, particularly 
with plant breeding, are those experiments which have been undertaken to discover 
the truth or falsity of Mendel's law of heredity. Investigations so far conducted 
with plants seem to confirm in most cases the mathematical law of transmission 
worked out by Mendel. A few observations on animals have also followed with 
some accuracy the same law. This law has been of the greatest value to plant 
breeders, and if it is found to apply with equal certainty to animal breeding, it may 
lead to exceedingly valuable results. It is important that its applicability to animal 
breeding should be tested at the earliest opportunity. Another law of transmission, 
which is undoubtedly very near the truth, is Gabon's "law of ancestral heredity." 
This law should be further investigated and its truth or falsity under varying condi- 
tions should be determined. 
ONE PLAN OF EXPERIMENTS. 
Many of the experiments so far undertaken have been imperfectly planned and 
their value has therefore been very much diminished. In investigating the many 
problems mentioned above, it is my opinion that reciprocal crosses with well-estab- 
lished breeds will yield the most valuable results. In investigating these problems 
it is highly important that we should start with at least two breeds of well-established 
characters. These should be reciprocally crossed, they should be bred purely, and 
they should be inbred. These experiments should be carried on coextensively and for 
a sufficient time to study the tendencies resulting from continued inbreeding, and these 
compared with simple pure breeding. In connection with these observations it is 
easily possible to study the influence of these methods of breeding upon prepotency. 
It will also give us an opportunity to study the relative influence of parents. The 
material secured ought to furnish us with the necessary data for studying Mendel's 
law, and ought to yield the data for examining into the law of ancestral heredity 
proposed by Gallon. These experiments may be so planned that the subject of tele- 
gony may be one of the problems under observation. 
The records of this experiment should show the mature weight in breeding condi- 
tion of every animal in the experiment. They should include photographs of the 
pure types resulting from the crosses. The birth weights should be carefully kept 
and studied Accurate measurements of the extremities, length of body, heart girth, 
size of skull, and other important measurements should be recorded. A careful 
study of these records ought to throw light upon Mendel's law, upon Galton's law of 
ancestral heredity, and on the effects of cross breeding, inbreeding, and the relative 
influence of parents. 
A STANDARD OF M EASRREMEXT. 
In the interpretation of the results of various methods of breeding we are greatly 
handicapped by reason of a lack of some standard of measurement. It has seemed 
to the writer for a long time that a step of first importance in breeding investigations 
is to settle upon some standard of measurement, Any measurements of mature 
animals are bound to be unsatisfactory by reason of variations, which may be due 
entirely to the result of environment. In studying the effects of inbreeding or cross 
breeding, it is necessary that we should separate these from all other influences 
whatsoever. In considering this question, the possibility of using the birth weight 
of animals has frequently suggested itself. The birth weight, perhaps, comes as near 
being an accurate measure of breeding influences as any other standard so far pro- 
posed. In any event it is worthy of consideration, and it is important that we deter- 
mine the conditions which control birth weight. 
The conditions which determine the birth weight of animals are not well under- 
stood, and investigators seem to have paid little attention to this classof facts. Under 
certain conditions the birth weight of animals seems to be closely associated with the 
subsequent growth and development of the young animal, and in general it may be 
said that a comparatively heavy birth weight is desirable. There is undoubtedly a 
