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 

 in many 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 case no 

 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 XXVII, 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 



