W. M. Aders 
207 
is conveyed from host to host by the ingestion of faeces containing 
resting forms. No parasites were observed in conjugation, nor could 
male or female forms be distinguished. 
Patton has drawn attention to the resemblance between Herpetomonas 
lygaei and the Leishman-Donovan body, and this flagellate also offers a 
similar resemblance, consequently it belongs to the same category. The 
flagellate stage is distinguished by the formation of a typical flagellum, 
and by division and multiplication of the flagellates. The non-flagellate 
stages closely resemble the Leishman-Donovan body, the parasite in the 
resting stage dividing into two parasites, which afterwards develope into 
two flagellated forms. 
For some time past there have been considerable differences of 
opinion concerning the ancestry of haemoflagellates. According to 
Minchin’s view the haemoflagellates were originally parasites of the 
intestines of vertebrates, from whence they wandered into the blood 
stream, and were taken up later by bloodsucking insects, thus becoming 
parasites of a vertebrate and of an invertebrate host. This hypothesis 
applies to many forms of haemoflagellates, but, as Prowazek pointed out, 
Herpetomonas muscae domesticae is a true parasite of the house fly; 
this insect is not a bloodsucker although its ancestors may have been, 
as a study of the mouth parts of the house fly appears to indicate. 
Herpetomonas aspongopi is likewise a true parasite of Aspongopus 
viduatus, which is not a bloodsucker. Many of the Hemiptera are 
fierce bloodsuckers, as for example the bed bugs ( Acanthia). The beak¬ 
like mouth-parts of the bed bugs bear a definite resemblance to the 
mouth-parts of the plant-feeding bugs, therefore it might be claimed 
that the ancestors of the latter were originally bloodsuckers, and that 
they had originally become infected with Plerpetomonad forms from 
some vertebrate host. 
I should like to thank Dr Balfour and Captain Archibald for their 
kind help and advice. 
