ZOOLOGY: R. ERDMANN 
509 
or eight. Figure 2 b shows such a multiple division. In these speci- 
mens only nuclei are present, but several hours later almost every animal 
has a nucleus and a blepharoplast. The latter individuals grow and 
divide (fig. 2 e). The nucleus has become smaller, the blepharoplast 
is still lying in the posterior end of the animal, but the distance between 
them has been diminished. Also the undulating membrane has disap- 
peared. Division into two animals is most frequent on the third and 
fourth day (fig. 2 d and f), and generally on the fifth day small individuals 
(fig. 2 e) with somewhat trypanoform appearance are numerous. On 
the fifth day round forms appear (fig. 2 g). That they are capable of 
division is shown in figure 2 h. These forms on the fifth and sixth day 
become motionless, and the flagellum encircles the animal. Often the 
staining capacity of the flagellum partially disappears, as is shown in 
figure 2 i. It is not necessary that the formation of these 'involution 
stages' last six days since sometimes three days after the trypanosome 
is taken from the rat, the stage as figured in figure 2 e is attained. 
These small forms are, by dark-field illumination, actively motile, and 
finally after the flagellum encircles the cell, gradually come to rest. 
The nucleus appears yellowish, the blepharoplast has a reddish yellow 
tinge. These characteristic stages are the last forms visible in plasma 
culture at 37° C. 
It seems probable that these forms found at the end of the cycle in 
the plasma similarly occur in the mammalian host, and in developing 
there give rise to the recurrent cycles of trypanosome form. This 
would be a general confirmation of the views of Moore and Breinl, that 
'latent bodies' observed by them in blood are the cause of the cyclical 
appearance of those trypanosome forms which they studied, i.e., Try- 
panosoma gambiense, Trypanosoma equiperdum, and Trypanosoma 
lewisi. This view affords plausible explanation of the reappearance of 
trypanosomes in the blood, and would eliminate the necessity of accept- 
ing a theory which implies the occurrence of parthenogenesis.^^ 
Strain M, February 13 to March 13, 1915. Culture kept at 16"" to 18°C. 
— After being 62 hours in the rat, the trypanosomes were transferred to 
the plasma medium, and kept at a temperature of 16° to 18°C. At this 
temperature the changes in the plasma medium do not proceed in as 
rapid a manner as at 37°C, the temperature of the mammalian blood. 
These were chiefly forms without granules (fig. 1, d and e). Figure 3, 
a and b, represents animals which have been forty-eight hours in the 
plasma. In these forty-eight hours no form changes are revealed by 
dark-field illumination, but frequently forms without a discernible 
nucleus are present (fig. 3 b). The wealth of granules is remarkable, 
