THE ''INHERITANCE OF ACQUIRED 

 CHARACTERS" IN TRYPANOSOMES 



By EDWARD HINDLE, Ph.D. 

 Beit Memorial Research Fellow ; Magdalene College, Cambridge 



Owing to their great economic importance the Trypanosomes 

 have been studied more closely than almost any other group 

 of the Protozoa. The result has been that they are found to 

 present many interesting biological features. One of the most 

 important discoveries is that these parasites possess the power 

 of responding rapidly to changes in external conditions and 

 of acquiring new characters which may continue during an 

 indefinite number of generations. Many papers have been 

 published on this subject recently, most of them devoted to 

 a consideration of the responses of trypanosomes to the action 

 of various medicaments. As the articles have been printed, 

 as a rule, in medical journals that are rather difficult of access 

 to most biologists, the writer has thought it desirable to collect 

 the more important results and to consider them from a general 

 point of view. 



(a) The Production of Mono-nuclear Trypanosomes by the 

 Action of Drugs. — It is well known that the size of the 

 kineto-nucleus in trypanosomes is subject to considerable 

 variation according to the species and that it varies from 

 the large rod-shaped kineto-nucleus of T. lewisi, the rat 

 trypanosome, to the minute spherical body representing this 

 structure in T equinum, the cause of " Mai de Caderas." 

 Werbitski, 1 however, was the first to notice that in some 

 races of trypanosomes the kineto-nucleus, which is supposed 

 by many writers to control the locomotor functions of the 

 parasite, was altogether absent. On examining a number 

 of races of T. brncei (Nagana) that had become resistant to 

 the action of certain drugs, he discovered that, in the case 



1 Werbitski (1910), " Uber blepharoplastlose Trypanosomen," Centralbl. f. 

 Bakteriologie, vol. liii. pp. 303-15. 



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