736 



SCIENCE 



[N. S. Vol. XXXII. No. 830 



humidity. A slight increase or a slight 

 decrease of temperature or humidity was 

 found to stimulate the action of the color- 

 producing enzymes, giving a tendency to 

 melanism ; but a large increase or decrease 

 of temperature or humidity was found to 

 inhibit the action of the enzymes, produc- 

 ing a strong tendency to albinism. 



A set of experiments was undertaken to 

 test the question whether coloration 

 changes induced by changed environ- 

 mental conditions were inherited, increased 

 or dropped in successive generations. 

 These experiments, carried on for ten 

 lineal generations, showed that the 

 changed conditions immediately produced 

 their maximum effect; that they were 

 purely somatic and were not inherited, the 

 progeny of individuals which had been ex- 

 posed to changed conditions through sev- 

 eral generations promptly reverting when 

 returned to normal conditions of environ- 

 ment. So far the results are confirmatory 

 of the well-established proposition that in- 

 duced somatic changes are not inheritable. 

 But it was found necessary to remove the 

 individuals experimented upon from the 

 influence of changed conditions during the 

 periods of growth and maturation of the 

 germ-cells. Potato-beetles emerge from the 

 pupa or from hibernation with the germ- 

 cells in an undeveloped condition, and the 

 ova do not all undergo their development 

 at once, but are matured in batches. The 

 first batch matures during the first few 

 days following emergence, then follows an 

 interval of from four to ten days, after 

 which the next batch of eggs is matured, 

 and so on. This fact made it possible to 

 test the effect of altered conditions on the 

 maturing germ-cells by subjecting its 

 imagos to experimental conditions during 

 the development of some of the batches of 

 ova and to normal conditions during the 

 development of other batches. 



In one of the experiments four male and 

 four female individuals of L. decemlineata 

 were subjected to very hot and dry condi- 

 tions, accompanied by low atmospheric 

 pressure, during the development and fer- 

 tilization of the first three batches of eggs. 

 Such conditions had been found productive 

 of albinic deviations in previous experi- 

 ments. As soon as the eggs were laid they 

 were removed to normal conditions, and 

 the larvffi and pupse reared from them were 

 kept in normal conditions. Ninety-eight 

 adult beetles were reared from these 

 batches of eggs, of which eighty-two ex- 

 hibited the characters of an albinic variety 

 found in nature and described as a species 

 under the name pallida; two exhibited the 

 characters of another albinic species named 

 immaculothorax, and fourteen were un- 

 modified decemlineatas. This gave a clear 

 indication that the altered conditions had 

 produced modifications in the germ-cells 

 which were expressed by color changes in 

 the adult individuals reared from them. 

 To prove that the deviations were not in- 

 herent in the germ-plasm of the parents, 

 the latter were kept under normal condi- 

 tions during the periods of development 

 and fertilization of the last two batches of 

 eggs; the larvae and pupse reared from 

 these eggs were similarly subjected to nor- 

 mal conditions, and gave rise to sixty-one 

 unmodified decemlineatas, which, when 

 bred together, came true to type for three 

 generations. The decemlineata forms pro- 

 duced under experimental conditions also 

 came true to type when bred together. Of 

 the pallida forms produced by experi- 

 mental conditions all but two males were 

 killed by a bacterial disease. These two 

 were crossed with normal decemlineata fe- 

 males, and the result was a typical Mende- 

 lian segregation, as shovm by the following 

 table : 



