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with its germ-plasm. The interest and importance of these 

 results is manifest, and it is well to remind ourselves once 

 more that they all emerge from the careful study of an 

 insect. 



Experiment 2. — Males and females of L. decemlineata were 

 subjected to hot dry conditions, and afterwards to normal 

 surroundings. During each period they deposited eggs. 

 From the eggs deposited in the second period, that of normal 

 conditions, pure decemlineata were bred for ten generations. 

 But from the eggs of the first period came many aberrant 

 forms, together with a certain number of apparently typical 

 decemlineata. These latter were reared side by side with the 

 decemlineata of the second period, which, as we have seen, 

 behaved in a perfectly normal manner throughout. But the 

 decemlineata of the first period, after giving rise to a genera- 

 tion of apparently quite normal forms, suddenly developed into 

 a race with an annual cycle of five generations instead of the 

 normal two, and continued to exhibit the same abnormality 

 up to the fourteenth generation, when the experiment ceased. 

 Here we have a physiological instead of a structural pecu- 

 liarity imposed upon the germ-plasm by artificial means, and 

 giving rise to a permanent race. It should be mentioned 

 that, in the words of Tower, " none of the beetles of the 

 lineata group, to which this beetle belongs, have more than 

 two, or rarely three, generations per year, and there are none 

 known in the genus that have over three." Another point 

 that emerges is that the application of the stimulus need not 

 always be immediately followed by the obvious response. In 

 the present experiment one whole generation elapsed before 

 the race began to show the effect of the abnormal treatment 

 to which its progenitors had been subjected. 



Experiment 3. — In another experiment with the same 

 species the conditions were varied by using heat in combina- 

 tion with moisture. In other respects the procedure was the 

 same. From the eggs of the second period eight successive 

 generations were reared, giving nothing but pure decemlineata. 

 From those of the first period, that of abnormal conditions, 

 came a large number of unmodified decemlineata and a certain 

 number of the form melanicum. Both of these forms bred 



