N. H. SWELLENGREBEL AND C. STRICKLAND 
385 
remains in the gut for a considerable time, thus affording a condition 
which seems to be particularly favourable for the production of a 
natural culture. 
Six Ornithodoros were fed on a rat in the chronic stage of infection 
with T. lewisi, and were dissected during the following days. It is 
particularly difficult to make good stained preparations of the gut 
contents. The large amount of sphaero-crystals from the malpighian 
tubes seems very unfavourable for the production of a good staining. 
Ornithodoros No. 1 (dissected after one day) and No. 2 (dissected after 
two days) showed only normal forms of trypanosomes, not worth 
mentioning. No. 3 (dissected after four days) contained trypanosomes 
showing different changes in the internal structure, which could only 
be interpreted as due to an incipient degeneration : hypertrophy of the 
blepharoplast (Diagram XX, Fig. 1), chromidia (Fig. 1), hypertrophy of 
the nucleus (Fig. 2), because the same phenomena are to be found in 
trypanosomes preserved in the refrigerator for 11 days. 
Diagram XX. G. 
Figs. 1—2. Flagellate out of the gut of Ornithodoros No. 3. 
Figs. 3—5. Flagellates out of the same tick, preserved for 24 hours in wet chamber. 
Figs. 6—10. Flagellates out of the gut of Ornithodoros No. 4. 
What remained of No. 3 was preserved in a moist chamber (at 
13—16° C.) for 24 hours. After that time flagellates were still present 
in the gut, but the form was altered, club-shaped. 
In stained preparations the hind end of the trypanosome was 
generally swollen up, the blepharoplast was situated in the neigh¬ 
bourhood of the nucleus (Fig. 5). Sometimes the blepharoplast even 
passed the nucleus (Fig. 4) so that a crithidia was produced. Degene¬ 
rative signs, as fragmentation of the nucleus, were often to be observed 
(Fig. 3). 
