2II 
presented by T. lewtsi, and the homologous phases occurring in the 
life cycles of T. gambimse and T. equiferdum. In each of these 
three cases the ‘ trypanosome form ’ multiplies through fission until an 
interaction takes place between the extra-nuclear centrosome and the 
nucleus. This interaction may be succeeded again by simple fission, 
Possibly this is also the case in T. gan/biense, 
while in T. lewisi it is followed by a series of rapid nuclear divisions 
resulting in the formation of the characteristic multi-nucleated masses. 
These differences, however, appear to be mere specific differences, of 
quite minor importance, which simply help to characterise in a specific 
sense the particular parasites we have considered. The divisions 
following the interaction between the extra-nuclear centrosome and 
the nucleus are, however, succeeded by a complete change of form, 
and by the assumption of the peculiar morphology of the round 
flagellated ‘latent body.' The fact that in T. equiperdum the latent 
bodies possess two flagella has probably a profound morphological 
significance, but it seems to be inappropriate at the present time, and 
in view of future work, to enter into a consideration of its actual 
significance. The details of the structure of the latent bodies, and 
their passage into the trypanosome form, is a matter which, although 
apparently simple in T. lewisi, is one which must receive further study. 
It is, for example, not at present clear in what way the two flagella of 
the latent body of T. equiperdum behave during this process. It 
becomes clear, when we consider the observations on the three forms 
to which we have referred, that during the life cycle in the blood the 
different phases in this cycle may become prolonged or shortened 
relatively with respect to one another. 
Thus the stage in T. gambiense, where one or two fissions possibly 
follow, the interaction between the extra-nuclear centrosome and the 
nucleus is prolonged in the case of T. e.qtiiperdum into a period where 
certainly several divisions take place, and this same period is again 
prolonged and rendered specifically characteristic in the case o 
T lewisi by the production of the large multi-nucleated masses. 
In this connection it seems also to be a very striking fact t at, 
whereas in the pathogenetic forms T. gambiense and T. equiper 
the phases of the life cycle as they appear among the trypanosome 
do so nearly simultaneously among all the parasites e. g 
io the blood at a particular time, and thus mark su 
p 
