SUBFAMILY HERPETOMONIN^ 



359 



5. Toxoplasma Nicolle and Manceaux, 1908. 



6. Piroplasma Patton, 1895. 



7. Achromaticus Dionisi, 1898. 



8. Hisfoplasma DdLvling, 1906. . - ' 



Unfortunately, there has been much confusion with regard to 

 these genera, due to lack of certain knowledge with regard to the 

 morphology and life-histories of the type species. The controversy 

 was keenest with regard to the points as to whether Herpetomonas 

 and Leptomonas Were or were not the same genus; whether Herpeto- 

 monas and Crithidia are good genera, or simply stages in the life- 

 cycle of a trypanosome. Briefly, the position is this: In 1851 

 Burnett discovered a flagellate in the house-fly, and called it Bodo 

 musccB-domesticce, for which Kent created the genus Herpetomonas m 

 1881; but two pages earlier in his book Kent created the genus 

 Leptomonas for a flagellate which Biitschli had found in the intes- 

 tine of Trilobius gracilis in 1876. The only distinguishing features 

 between these two genera are the presence of a contractile vacuole 

 and the flexibility of the body in Herpetomonas, but modern research 

 fails to confirm the presence of this contractile vacuole in Herpeto- 

 monas, and flexibility per se is insufficient to separate the two 

 genera. Prowazek, however, in 1904, emended Herpetomonas, 

 describing H. musccB-domesticce as possessing two flagella united by 

 a membrane, and arising from a flagellar-situated diplosome; but 

 Patton, in 1909, and Mackinnon, in 1910, have demonstrated 

 that this is merely a stage in the division of H. muscce-domesticce ; 

 and Chatton and Leger, in 1911, demonstrated that there was an 

 axostyle present in Leptomonas drosophilce; and Chatton later showed 

 that the diplosome of H. muscce-domesticce was merely the remains of 

 this axostyle. Therefore it would appear that the two genera are 

 indistinguishable, and might therefore be united, and, if so, the older 

 name Leptomonas Would by the law of priority come into use, to the 

 exclusion of the name Herpetomonas ; and this may happen, but it 

 cannot be adopted at present, because the type species of the genus 

 Leptomonas — namely, L. butschlii Kent, 1881 — has, as yet, been 

 incompletely studied, and may eventually be found to be the same 

 as, or different from, Herpetomonas / therefore we continue to retain 

 the two genera Herpetomonas and Leptomonas in the same condition 

 as in our last edition — -that is to say, indistinguishable from one 

 another. 



With regard to the controversy as to whether there is a genus 

 Crithidia or not, the answer is much simpler. There can be no doubt 

 that crithidia-like forms exist in the life-cycle of many trypano- 

 somes; but the work of Patton, Porter, and Swingle has clearly 

 shown that there is a separate genus, CrithidiaLegev, 1902, emended 

 Patton. Further, we believe that Miss Porter is correct when 

 she states that Crithidia should be placed in the family Trypanoso- 

 midse on account of the presence of an undulating membrane. 



With regard to Leishmania, a better knowledge of the life-history 



