S. R. Christophers 
47 
Bielitzer’s tig. 18, PI. VI, shows what is evidently a club-shaped body in 
process of formation as described on page 57 of my paper. The upper 
part of fig. 19 also shows the achromatic line to which I have referred, 
and the same line (indicating the formation of the tail of the club- 
shaped body) can be seen in several of the groups of parasites shown in 
fig. 17. 
That the double bodies formed in the gut are not conjugation forms 
(as considered by Koch and Marzinowski and Bielitzer) is shown by the 
fact that these become not one but two vermicules. My explanation 
of this appearance is simply that a parasite on the point of division or 
already partly divided has taken on development. All the appearances 
seen favour this view. 
I have also followed very clearly the change of the club-shaped bodies 
after they have embedded themselves in the yolk substance of the egg 
or, as happens when parasites are taken in during the nymphal stage, 
when they have penetrated the substance of tissue cells composing the 
embryonic-like mass, which models, as it were, the body of the adult tick 
within the skin of the nymph. 
In both cases the persistence of the peculiar structure carried at the 
anterior end of the club-shaped body, and the fact that the sharp pointed 
tail can often be seen for some time projecting from the globular mass 
characteristic of the next stage, make any error of interpretation 
improbable. There follows then upon the club-shaped body, which 
suggests the ookinite, a stage of great growth within the substance of a 
cell. The arrangement of the chromatin in this stage clearly shows that 
an ultimate breaking up of the mass is intended. The appearances are 
not very dissimilar in fact to the earlier stages in the “ zygote ” of 
malaria as figured by Marchiafava and Bignami. 
The appearances figured by Marzinowski and Bielitzer and referred 
to in the passage quoted as possibly being cells of the tick are clearly 
cells that have been invaded and almost converted into the products of 
division of the parasite. The figures recently given by Dschunkowski 
and Luhs(9) and others of Theileria multiplying in the tissue cells show 
exactly similar appearances. 
The final accumulation of “ sporozoites,” or “ spores ” as they are 
termed by Marzinowski and Bielitzer, in the salivary acini is another 
undoubted stage. The figures given by Marzinowski and Bielitzer of 
these bodies showing stellate and oval fornis closely resemble those 
figured in my own work. The only observation of these authors at 
variance with mine is the finding of club-shaped bodies in the saliva of 
