OX THE TRYPANOSOME OF THE LITTLE OWL. 
173 
least), 1 breadth 41 fi , free flagellum 7 /x (at least), and aflagellar 
portion 6 /u. It will be seen that from medium-sized forms, 
such as those of figs. 6, 17 and 5 (which have not attained the 
extremely elongated appearance presented by this type, when 
fully developed), it is a very slight step to the “blue” forms 
of figs. 9 and 23. 
The latter type arises, we should say, principally by an 
increase in bulk or density of the general cytoplasm of the 
body, which results in a distinct alteration in its staining 
reaction (chiefly by Giemsa). It is important to note that 
this in no way involves a contraction in length, i.e. there is 
no shortening of the body to compensate for increased stout- 
ness. On the contrary, in the larger individuals the whole 
body, including the aflagellar portion, is found to have 
increased in length as well as in width or bulk. We shall 
have to refer again to this point when subsequently criticis- 
ing Zupitza's paper. 
In the later owls (Nos. 19 and 23) the trypanosomes are in 
a quite different phase — that is to say, the parasites are in what 
we regard as the summer condition. We have not observed 
any individuals either of the slender, medium-sized variety, 
or of the large blue type; both these forms appear to be 
entirely absent. Neither do most of the parasites present in 
these later owls quite correspond to the small forms occurring 
in the earlier birds, though in all probability they are 
developed from the latter type. 
The summer forms of trypanosome (figs. 12, 13, 29-31, 
40-42) are all fusiform and stumpy in character, with the 
kinetonucleus situated near the abruptly pointed afiagellar 
end; nearly all the individuals observed, however, are dis- 
tinctly larger than the small forms above described. More- 
over, the body, instead of being a fairly slender spindle, is, in 
most cases, comparatively thick or stout in proportion to its 
length. This character may appear to be very marked, both 
1 The total length of the parasite, as also the length of the free 
flagellum, is probably a few fi longer, since the end of the flagellum 
pasess over the nucleus of a blood-cell, where it cannot be traced. 
