NEW SPECIES 97 



point of heat or of cold the color of each next generation of 

 beetles grew darker and richer, but that when either the heat 

 or the cold was greater, the color grew lighter from one 

 generation to the next, until it had quite faded out. 



These experiments proved that the temperature of the sur- 

 roundings in which beetles live and multiply influences the 

 power of their germ cells to pass on shades of color to the 

 next generation. 



Dr. Tower was in the midst of these experiments when a 

 serious calamity brought them abruptly to an end. Beetles' 

 eggs with long pedigrees behind them were in the green- 

 house waiting to be hatched. Young beetles with pedigrees 

 quite as long were feeding and growing. Full-grown beetles 

 were in fine condition. It was one of the hottest days in the 

 summer of 1904. Workmen were repairing the heating ap- 

 paratus of the university, and, not knowing what might hap- 

 pen, they turned the heat on at full pressure. Soon every 

 beetle was killed ; every egg was put beyond the power of 

 hatching. The record of these studies had to be closed. 

 Dr. Tower had to make a new start with his investigations, 

 and then it was that he printed his book and reported results 

 up to the date of the overheating. 



Still, even before the heat killed the beetles, another set 

 of experiments had been going on which were of vast im- 

 portance to biologists. Dr. Tower wished to know whether 

 or not it makes any difference to the next generation if beetle 

 parents are put into an unusual environment just before they 

 lay their eggs, and at no other time. 



He suspected that germ cells might be influenced by their 

 environment while the body was getting them ready to be 

 laid. If this were so, he knew that one set of eggs would be 

 affected at a time. 



