C. Strickland 
The sj^orozoite (Fig. 2)^ as seen free in the lumen of the midgut, is 
a sickle-shaped body about 4-4'5 /x in length by 1 /u, in breadth. It 
consists of a very hyaline cytoplasm, without any partition, suri’ounding 
a nucleus. The latter is rather variable in position and appears to 
consist of a homogeneous oval mass of chromatin. The organism does 
not seem to possess any power of active movement: it doubtless enters 
an epithelial cell of the midgut, as is the case in related species, and 
grows there. 
The small trophozoite (Fig. 3) is the next stage of development found 
in the midgut of the hea larva and it is eitlier attached to an epithelial 
cell, or lies free in the gut. These free forms may only be free by 
virtue of the manipulations to which they are subject, but it is probable 
that the parasite can disengage and reattach itself at will. The small 
trophozoite is completely differentiated into epimerite, protomerite, 
and deutomerite. Its dimensions are about 12'5-1G'5 x 'b fx. In 
Fig. 2. 
Fig. 4. 
Fig. 3. 
Fig. 2. Sporozoites. 
Fig. 3. Young trophozoites (a) attached to epithelial cell, the nucleus of which is 
shrivelled, (&) free. 
Fig. 4. Nucleus of small trophozoites. 
structure the cytoplasm is differentiated into ecto- and endoplasm, 
in the latter of which lies a small spherical nucleus (Fig. 4) limited by 
a nuclear membrane, and consisting of a lightly staining material 
containing in its centre a small sphere of chromatin formed by a close 
skein of this material (see Fig. 4). 
The adult trophozoites (Fig. 5). All stages of the growth of the 
trophozoite are met with, and occur either attached or free. The 
arbitrarily selected type is about 55 p long. The epimerite is sym¬ 
metrical and cup-shaped with many labile digitations (Fig. 6) and is 
connected to the protomerite by a narrow neck. The bottom of the 
depression of the epimerite appears to be sometimes protruded slightly 
in the form of a small cone. The cytoplasm of these forms consists 
' The figures given in the text are not drawn to the same scale; the correct dimensions 
are given in the text. 
7—2 
