228 PROTOZOOLOGY 



which are produced under the influence of certain environmental 

 conditions. Jollos designated these changes long-lasting modifica- 

 tions (Dauermodifikationen) and maintained that a change in en- 

 vironmental conditions, if applied gradually, brings about a change, 

 not in the nucleus, but in the cytoplasm, of the organism which 

 when transferred to the original environment, is inherited for a 

 number of generations. These modifications are lost usually during 

 sexual processes at which time the whole organism is reorganized. 



The long-lasting morphological and physiological modifications 

 induced by chemical substances have long been known in parasitic 

 Protozoa. Werbitzki (1910) discovered that Trypanosoma brucei 

 loses its blepharoplast when inoculated into mice which have 

 been treated with pyronin, acridin, oxazin and allied dyes, and 

 Piekarski (1949) showed that trypaflavin and organic metal com- 

 pounds which act as nuclear poisons and interfere with nuclear di- 

 vision, also bring about the loss of blepharoplast in this trypano- 

 some. Laveran and Roudsky (1911) found that the dyes mentioned 

 above have a special affinity for, and bring about the destruction 

 by auto-oxidation of, the blepharoplast. Such trypanosomes lacking 

 a blepharoplast behave normally and remain in that condition during 

 many passages through mice. When subjected to small doses of cer- 

 tain drugs repeatedly, species of Trypanosoma often develop into 

 drug-fast or drug-resistant strains which resist doses of the drug 

 greater than those used for the treatment of the disease for which 

 they are responsible. These modifications may also persist for several 

 hundred passages through host animals and invertebrate vectors, 

 but are eventually lost. 



Long-lasting modifications have also been produced by several 

 investigators by subjecting Protozoa to various environmental in- 

 fluences during the nuclear reorganization at the time of fission, 

 conjugation, or autogamy. In Stentor (Popoff) and Glaucoma 

 (Chatton), long-lasting modifications appeared during asexual divi- 

 sions. Calkins (1924) observed a double-type Uroleptus mobilis (Fig. 

 95, b) which was formed by a complete fusion of two conjugants. 

 This abnormal animal underwent fission 367 times for 405 days, but 

 finally reverted back to normal forms, without reversion to double 

 form. The double animal of Euplotes patella (d) is, according to Kim- 

 ball (1941) and Powers (1943), said to be formed by incomplete di- 

 vision and rarely through conjugation. De Garis (1930) produced 

 double animals in Paramecium caudatum through inhibition of di- 

 vision by exposing the animals to cyanide vapor or to low tempera- 

 tures 



