150 SUMMARY [CH. x 



it exhibits. It is no less true that the process of transmutation 

 only differs in degree from the process of evolution. Here it 

 is a question of the rapidity of the change. 



Let us take by way of illustration the case of a family of 

 ancient lineage, the members of which hold high office in the 

 State and are remarkable for their wealth and erudition. 

 Such a family may have sprung 500 years ago from humble 

 origin and, while the fortunes of one branch have steadily 

 prospered and successive generations have gradually acquired 

 fame and amassed wealth, the original yeoman stock from 

 which it sprang has continued to be represented throughout 

 the centuries, in some corner of the kingdom, by men chiefly 

 remarkable for their deficiency in the riches and learning and 

 reputation for which the others are distinguished. It is con- 

 ceivable that a son of the older and less distinguished branch 

 of the family, seizing a favourable opportunity, might, by the 

 exercise of the same faculties of industry and thrift displayed 

 by the others, raise himself in the space of a single life-time to 

 a position of wealth and power equal to theirs. We can trace 

 the steps by which, in the course of time, a virulent and highly 

 specialised race of bacteria has been evolved from a less 

 virulent and less highly organised race. We find the two races 

 living still side by side. The question arises whether it is pos- 

 sible under unusually favourable conditions for the process of 

 adaptation and specialisation to take place with such rapidity 

 as to suggest a sudden transmutation. 



The conversion of the saprophytic pneumococcus into the 

 parasitic pneumococcus by Eyre, Leatham and Washburn 

 (vide p. 115) appears to offer an example. These observers 

 describe the virulent parasitic pneumococcus as requiring for 

 its growth a certain reaction and temperature and particular 

 media (blood agar); it would not grow if the reaction were 

 even faintly acid or at a temperature much below 37 C. and 

 rapidly died out on agar or in broth. It would not liquefy 

 gelatin and in broth formed a dust-like deposit. The avirulent 

 saprophytic variety, on the other hand, grew luxuriantly at 

 temperatures ranging from 37 to 20 C., on agar, gelatin, 

 potato or in broth, whether acid or alkaline, slowly liquefying 



