D. L. Mackinnon 
269 
Some of the flagellates that I tried to cultivate on agar-agar 
continued to live for three or four days, but showed no signs of 
multiplication. They all assumed the form of the flagellates under the 
sealed-down cover-slips— i.e. the body had become pear-shaped and the 
kineto-nucleus had travelled back into the body, drawing the flagellum 
with it. 
Herpetomonas or Leptomonas ? 
I believe that the above account throws lisrlit on the value of certain 
o 
so-called generic characters brought forward in the recent discussion on 
the classification of the herpetomonads and their allies. 
It is necessary to recapitulate briefly. From his observations on the 
flagellate of Musca domestica, Prowazek was led (1904) to state that the 
genus Herpetomonas, Kent, possessed a double flagellum. 
Patton (1909) showed clearly that this view was erroneous, the two 
flagella occurring only in individuals in course of longitudinal division. 
In support of this he mentioned that if a sufficient number of flies be 
examined, it will be found that, while in some of them almost all the 
flagellates have a double flagellum, in others the majority have a single 
flagellum. Further, in tracing out the life-history he showed that the 
pre- and post-flagellate stages have only one flagellum. Patton has 
described many other herpetomonads from various insect hosts, and 
these he finds fall in line with the flagellate of the fly. He therefore 
includes them all under Herpetomonas, that is, a trypauosomatid 
having a single flagellum, and with the kineto-nucleus placed some 
distance in front of the tropho-nucleus in the adult form. Donovan 
(1909) and Porter (1909) confirm Patton’s statements. 
Prowazek (1909) repeats his statements, and still holds to the view 
that Herpetomonas, sensu stricto, is a bi-flagellate. Still more confusion 
has recently been brought in by the repeated attempts of certain of the 
French school—notably Chatton, Alilaire, and Roubaud—to support 
Prowazek’s view by splitting up the genus Herpetomonas into two. 
They would revive Leptomonas, Kent for such forms as have one 
flagellum and no rhizoplast, reserving Herpetomonas for those with a 
double flagellum and a rhizoplast. 
These authors are very doubtful about the value of Patton’s 
definitions of the genera Crithidia and Herpetomonas, contending that 
the presence of an undulating membrane and the relative positions of 
the kineto- and tropho-nuclei are features too variable to be depended 
on. Chatton and Alilaire (1908—1909) prefer to base their classification 
