E. Hindle 
471 
spirochaetes and also into fusiform bacilli has been repeatedly observed 
in the tick. If an infected Argas be kept at a temperature of 37° C., 
after about five days spirochaetes appear in the coelomic fiuid, the lumen 
of the gut, and all the organs of the tick. By making a series of films 
commencing with the unincubated tick and ending with those containing 
fully developed spirochaetes, all the stages in the development of the 
latter forms from the coccoid bodies may be obtained. 
The effect of heat on the development of the intracellular coccoid 
bodies is rather variable and does not always result in their development 
into spirochaetes. The first effect seems to be the production of growth 
and transverse fission, resulting in the production of large masses of 
^ 0 ^ ]) 
Fig. 4. Stages in the development of sjDirochaetes 
from the coccoid bodies. 
coccoid bodies that simulate schizogony. Subsequentl}'^, certain of 
the coccoid forms elongate, first assuming a bacillus form, and then 
appearing as short spirilla (Fig. 4). Some of the bacillus forms merely 
elongate into long fusiform bacilli which are usually intracellular. The 
short spirilla escape from the cells into either the lumen of the gut and 
Malpighian tubules, or into the coelomic fluid, and there grow in length 
until they appear as normal spirochaetes (Fig. 4). The various stages 
in their elongation up to the normal spirochaete have been repeatedly 
observed in the tick and, therefore, it may reasonably be assumed that 
the same form of development occurs when the coccoid bodies are 
introduced into the blood of a fowl. As the spirochaetes appear in the 
coelomic fluid of a tick which has been incubated at 37° C. for a few 
