SOME EECENT WORK ON MUTATION IN 

 MICRO-ORGANISMS. 



By CLIFFORD DOBELL. 



Much work has been done in the last few years upon mutation" 

 in several different groups of micro-organisms. This work has been 

 published in many different places, and has been largely carried out 

 in connexion with investigations of a medical nature. The records 

 are therefore somewhat diffuse, and not always easily accessible to 

 the biologist who applies himself mainly to the study of genetics. In 

 the compass of the following few pages I shall endeavour to chronicle — • 

 in a somewhat critical spirit — some of the more important observations 

 which have been recently recorded in this branch of biology. 



I. Mutations in Tkypano.somes. 



In this first section, I shall describe some recent work upon mutation 

 phenomena observed in several species of flagellate Protozoa belonging 

 to the genus Trypanosoma. The mutations may be grouped in two 

 different classes — morphological and physiological. 



A. Morphological Mutations. 



In several cases, structural modifications have been induced in 

 Trypanosomes, and found to be permanent and transmissible for a 

 variable number of succeeding divisions. These cases will now be 

 described. 



1 I use this term — as others have ah-eady done — to denote those heritable modifications 

 which have been induced in various ways in various micro-organisms. I believe that 

 a " mutation " in a Trypanosome is essentially the same sort of thing as a "mutation " in 

 a multicellular organism. But I must also point out that I use the words "inheritance," 

 " heritable," and similar terms in the customary manner — applying them to the trans- 

 missible characters of such organisms as Trypanosomes, Bacteria, etc. I do not wish to 

 assert, however, that "inheritance" in Trypanosomes means exactly the same thing as 

 " inheritance " between parent and offspring in sexual multicellular organisms. 



