ACQUIRED CHARACTERS IN ANIMAL BREEDING 493 
were darker than the females. There is a real distinction between this 
and similar cases of parallel induction, where the stimulus acts directly 
upon the germ cells, and the supposed action of a stimulus through a 
somatic modification on the germ-plasm. So far as practical breeding 
operations go this matter perhaps has little importance save in relation 
to disease and immunity, under which head it will be discussed later. 
The problem comes up for the most part in connection with the effect 
of adverse conditions upon the individual. Thus conceivably alcoholism 
inmany cases may result in such a thorough poisoning of the entire system 
that body and stirp are both injured. In consequence offspring of such 
parents might display structural peculiarities and defects, similar to or 
different from those produced in the parent by the same adverse condi- 
tions. Certain experiments on the effects of alcohol on the progeny of 
animals furnish the direct evidence of parallel induction. Stockard’s 
investigation with guinea-pigs led to the conclusion that ‘‘mammals 
treated with injurious substances such as alcohol, ether, lead, etc., 
suffer from the treatments by having the tissues of their bodies injured. 
When the reproductive glands and germ cells become injured in this 
way they give rise to offspring showing weak and degenerate conditions 
of a general nature and every cell of these offspring having been derived 
from the injured egg or sperm cell is necessarily similarly injured and can 
only give rise to other injured cells and thus the next generation of off- 
spring is equally weak and injured, and so on... This might be 
construed to show the transmission of acquired characters, but it 
cannot be properly interpreted in such a sense. There is in this caseno 
transmission of a new or strange character strictly speaking, merely a 
weakened or injured cell gives rise to other weak cells.” On the other 
hand Pearl, working with chickens, reaches the conclusions, (1) “that 
the progeny of alcoholized parentage while fewer in numbers is made 
up of individuals superior in physiological vigor, and (2) that this result 
is due to a selective action of the alcohol upon the germ cells.”” Nice, 
also, who worked with white mice, fails to observe any injurious effect 
from alcohol in fertility or vigor of growth and but a small one in via- 
bility. Thus the evidence now available would certainly indicate that 
it is dangerous to draw far-reaching conclusions as to the general effects 
of poisons on the germ cells from data obtained on a single species. 
Modern breeds of livestock without question trace back to extremely 
diverse foundation stocks. This historical fact has been discussed very 
inadequately in Chapter X XVII, and it has been shown specifically in 
some cases that the potentialities for high performance existed early in 
the breeds. Accordingly the constant practice of breeding from the best 
has resulted in the elimination from the line of descent of a large propor- 
tion of those animals which have failed to measure up to the standard 
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