204 Mutation in Micro- Organisms 



in the size of the Trypanosomes was also brought about by passing 

 them through beetles {Gychrus rostratus and Aphodius sp.), or through 

 a slug (Aiion impiricorum), and then back again into rats^ Several 

 other passages (axolotl, caterpillars, etc.) were unsuccessfully attempted. 



Wendelstadt and Fellmer made similar experiments with T. lev/isi. 

 They succeeded in passing this species from the rat through lizards, 

 frogs, and grass snakes. In the cold-blooded host, no Trypanosomes 

 could be found microscopically after inoculation : but inoculation of 

 the blood back into uninfected rats gave rise in them to an infection 

 with parasites of increased size^ When the normal Trypanosomes 

 (Fig. B, 4) from the rat were passed through a snake, or through a 

 snake and then a frog, and then back into a rat, a remarkable modifi- 

 cation was finally produced. The Trypanosomes were not only much 

 larger, but they were also greatly elongated at the aflagellar end^ 

 (Fig. B, 5). No divisions were observed in these forms. Moreover, 

 they showed certain differences in their staining properties as compared 

 with the original forms. 



It may be added that no results similar to these of Wendelstadt and 

 Fellmer have been recorded by other workers. 



A much more interesting — because more thoroughly investigated — 

 morphological mutation in Trypanosomes has been discovered by Wer- 

 bitzki (1910). In the course of some researches on the effects of 

 certain organic dyes upon living Trypanosomes, this worker made the 

 following observations. (The researches were carried out in Ehrlich's 

 laboratory, on a strain of T. brucei known as " Nagana ferox," and cul- 

 tivated in mice.) When certain dyes were injected into infected mice, 

 the Trypanosomes (Fig. C, 2) lost their kinetonuclei (Fig. C, 1). The 

 modified Trypanosomes were found to remain permanently devoid of 

 this organ during subsequent divisions. They divided normally and 

 actively, and could be passed in the usual way through other mice by 

 subinoculations. A race of Trypanosomes with a permanent morpho- 

 logical modification has been thus produced. The dyes used successfully 



1 The blood containing the Trypanosomes was injected into the body of the invertebrate, 

 which was subsequently ground up in salt solution and the liquid so obtained injected into 

 a rat. It is somewhat surprising that any positive results were obtained by such crude 

 methods. Besides the Trypanosomes, very many other things must have been injected 

 into the rats. 



2 The incubation period in the rat was also found to be shortened. 



3 Forms similar to these are of constant occurrence during the multiplication period of 

 normal T. lewisi in the rat (Minchin). They have been described as a distinct species 

 (" T. longocaudense ") by Lingard. 



