466 
cleate condition, but that the large, principal nucleus is double (figs. 1—8). 
Several of these individuals show the small chromatic element in ad- 
dition, and in such cases this also is usually double (figs. 2 and 3). The 
position of the two nuclei vis-à-vis of each other varies considerably, 
as will be seen from the figures. The line joining them may be approx- 
imately parallel either to the short or the long axis of the parasite, or 
it may run obliquely. In the intermediate-sized forms the body certainly 
appears single; so far as the cytoplasm is concerned there is not the 
least indication that two individuals are present. This is the case also 
in some of the larger parasites (figs. 4—7). Apart from the double 
character of the nucleus the parasites are typical Halteridia, both as 
regards general form and contour and the position in the corpuscle. In 
other large forms, however, the cytoplasm shows a distinct split, usually 
running more or less longitudinally through the middle of the body. 
This split is either incomplete (fig. 12) or practically complete (figs. 9,10); 
in the latter case the appearance is presented of two individuals, each 
with a single nucleus, the two parasites lying parallel to each other on 
the same side of the blood-corpuscle, between the nucleus and the longer 
edge, i. e. in the customary position. 
Parasites such as those described occur fairly frequently in the 
first preparations made. In the next smears prepared, however, five 
days subsequently, while Halteridia showing this condition are still 
present, they are much more infrequent — rather scarce, in fact. And 
in preparations made ten days later again, I have not observed any para- 
sites with the double nucleus. 
On first studying this condition, I thought the most likely ex- 
planation was that it represented different stages in the binary fission 
of a single individual. This seemed indicated by the fact that in the 
intermediate-sized forms, the body appears single, although possessing 
two nuclei, and only in the large examples is a splitting of the cytoplasm 
apparent. After prolonged examination of my slides, however. I have 
come to the conclusion that this cannot be the correct explanation in 
some cases, at any rate, for I have been able to find two or three para- 
sites in which the double-nuclear condition is present, where one of the 
two nuclei is distinctly male in character and the other female; i. e., one 
is large and diffuse and stains bright red, the other small, compact and 
stains a darker red (figs. 11 and 12). Moreover, the cytoplasm in one part 
of the body, on the side of the female nucleus, may be denser and stain a 
somewhat deeper blue that that in the other half of the body, in which 
the male nucleus lies. The limit or periphery of the body of the para- 
site is quite even and regular and has the typical contour of an adult 
ordinary individual. Nevertheless, it is obvious that, in such cases, there 
