Lary LracL ut a fly, and become cysts eitlier in its colon or rec¬ 
tum. 
4. 1 ire cysts wiien ingested deveiop in a few iiours into long 
tiageliates wnuli inultipi)- as ctescribed above. 
5. The food ot tlie house fly play s an important part in the life 
history of Herpctumoîias miiscae domcsticae. 
b. 'Ihis flagellate lias tliree different stages, prejLagelUite, jla- 
gellaic and posl-jiageLluLe, and in noue of these bas it a double 
ilagellum. 
7. in the early stages of the infection the parasites are seen 
as typical herpetomonads with the blepharoplast lying close to 
the anterior end ; they then hâve the appearance described by 
some authors as being characteristic of the genus Herpetomo- 
nas (Kent). In a later stage they are long slender bodies with 
well developed single flagella, and v\ould then belong to the ge¬ 
nus Leptomunas of Chatton, and in a still later stage {pro-encyst- 
ing jorms) the blepharoplast moves close to the nucléus and 
even passes behind it. 
1 canriot too strongly emphasize the importance of this last 
point, as 1 find Kleine in his most recent paper States that mam- 
malian flagellâtes (trypanosomesj in the stomach of tsetse flies 
can be distinguished from true insectan formis by the position 
of the blepharoplast. In the case of Herpetumunas miiscac do- 
mesticac we hâve a parasite which exhibits at one time the so-call- 
ed characteristic appearance of an insectan flagellate, and at 
another stage that of a mammalian tr}'panosome when taken into 
an insect’s stomach. 
In stiKhhng these flagellâtes in experimentally infected insects 
it is of the utmost importance to describe in detail every morpho- 
logical variation for it is only then possible to understand the 
different appearances which may be seen. 
By stLidying Hcrpetomonas jniiscac domcsticac, the type spe- 
cies of the genus Herpetonionas in the way I hâve described 
above, l hâve been able to work ont its complété life cycle, and 
at the same time to ascertain exactly how it is transmitted in na¬ 
ture. 1 intend applying the methods in studying the life his¬ 
toriés of about twelve new flagellâtes 1 hâve foiind in flies, bugs, 
ticks and flies. One of the flies, a Sepsid, contains a Crithidia 
as well as a Herpetonionas, this insect feeds entirelv on cow 
dung. Most of these parasites, however, occur in non blood stick- 
