386 
Trypanosoma lewisi 
Ornithodoros No. 4 was dissected on the sixth day of the experiment. 
The flagellates found in the gut were very slender and showed hyper¬ 
active motion. In stained preparations most of them had two nuclei 
with the blepharoplast situated between them, exactly as in the forms 
we found in the culture between slide and cover-slip in the beginning of 
Series F (Diagram XX, Figs. 8—10). 
Sometimes both nuclei are equally well developed (Fig. 8); some¬ 
times the posterior nucleus seems to be degenerating, and in other 
cases both of them are very abnormal (Fig. 10). Beside these forms 
we found also long slender flagellates with the blepharoplast at the side 
of nucleus (Fig. 7), but no real crithidiae were to be found. 
Fig. 6 shows a not infrequent type with the blepharoplast just 
behind the nucleus, the hind end being filled with dark-staining 
granules. 
This tick No. 4 had been put in the incubator (22° C.) for two 
days in the hope of stimulating development, but it is possible that 
by this manipulation we only hastened the process of degeneration, 
for the gut of the same tick preserved in a moist chamber in the 
incubator for another night, did not contain any flagellates. Tick 
No. 5, put in the incubator for three days, and dissected seven days 
after feeding, did not contain any active flagellates. A like result was 
obtained with tick No. 6, dissected after eight days; this tick was put 
in the incubator for three days and then replaced at 13—16° C. for 
one day. 
The trypanosomes are consequently kept alive in the gut for six 
days, in which time they undergo degenerative changes very much like 
those occurring in trypanosomes kept for some time in the refrigerator, 
i.e. the gut is not favourable to any development but checks the growth 
of bacteria, which should otherwise have destroyed the trypanosomes 
much sooner. It is an interesting fact that although there is no 
development in the tick, the longevity there is greater than in the 
louse, where development takes place 1 . 
6. Development of T. lewisi in the gut of Acanthia 
lectularia (bed bug). 
Our observations in this connection are incomplete, nevertheless they 
appear worth recording. As controls thirteen bugs were dissected to 
1 There being no development at all, controls were not necessary; the crithidiae found 
in tick No. 3 cannot be considered as developmental. 
