340 



CIVIC BIOLOGY 



of these try to find valuable variations in the neighborhood. 

 Our native nut trees have been neglected in this matter, and 

 the Department of Agriculture is calling for a special search 

 of the entire continent for valuable varieties. With the whole 

 country organized for the search and with breeding in control 

 of experts, we may hope for better progress in every line of 

 plant and animal improvement than ever was known before. 

 Injury of germ plasm. Germinal substance is, of course, 

 obliged to draw its nourishment from the body ; hence we 

 may expect to find vigorous germs in strong, healthy bodies. 

 Animals that become too fat are likely to have enfeebled 

 germs or to be totally sterile, and conditions that show no 

 appreciable injury to the body may prove fatal to the germ 

 plasm. This is seen in Stockard's experiments with alcohol 

 tabulated below: 



EXPERIMENTS WITH GUINEA FIGS TO TEST INFLUENCE OF ALCOHOL 

 ON GERM CELLS 



The germ cell from each parent builds half the embryo, and 

 the twenty-four matings in which the sperm alone is alcohol- 

 ized are a proof that an alcoholized sperm cell of a guinea 

 pig cannot do its share toward building up a normal offspring. 1 



1 Stockard allowed the guinea pigs to breathe fumes of alcohol for one 

 hour a day, six days in the week. The animals showed no outward injury, 

 in fact they gained somewhat in weight. 



