18 PROF. E. A. MINCHIN ON PROTOZOAN [Jan. 12, 
stages similar to the vermicules; I found, however, in the large 
uninucleate * leucocytes, bodies which I Aue at Aret to be para- 
sites: rounded bodies staining a faint pink (after Giemsa’s stain), 
with a central darker grain or two such grains (figs. 17-19). I 
could not find, however, anything in the least transitional to the 
vermicule-like bodies, and I do not think now that the bodies in 
the leucocytes are of parasitic nature. In the corresponding 
leucocytes of the tench (figs. 45-48) there are to be found 
commonly, but not invariably, round pink-staining bodies, some- 
times a single one of variable size, sometimes two, three, or four 
such; they are clearly vacuoles containing some substance which 
has stained, probably, with the eosin of the Giemsa stain, and I 
think it very probable that the bodies in the leucocytes of the 
perch are of a similar nature. 
If the vermicules, however, are not stages of a hemogregarine, 
in what light are we ‘tor egard them ¢ Since they were found in the 
same blood as the encysted trypanosome already described (fig. 15), 
the idea occurred to me that perhaps the stout forms of Zrypano- 
soma perce might eneyst in the internal organs and undergo 
multiplication to form the vermicule-like bodies : these in their 
turn might acquire flagella and so give rise to the smallest forms 
of the trypanosome, which by growth into the large forms would 
complete a cycle of multiplication in the fish. The rarity of 
fission-stages of the trypanosomes of fish is remarkable; I have 
never seen a fish-trypanosome in division, but Laveran and 
Mesnil have described fission of 7’. remaki in two pike infected 
artificially, and Lebailly and Franga have, as stated elsewhere, 
described fission in 7’. granulosum from cultures in vitro. It is 
therefore quite possible that fission may be a process restricted to: 
certain parts of the life-cycle, and that the usual mode of multi- 
plication in fish-trypanosomes may be such as I have indicated 
above. In Zrypanosoma lewisi, for example, fission is only found 
during the first week or so after moculation; there is then no. 
further multiplication, the trypanosomes being all of one size and 
type. On the other hand, tish-trypanosomes usually exhibit 
marked variations in size which are very suggestive of growth 
from the smallest to the largest forms. I desire to make this 
suggestion cautiously, as the data on which it is founded are 
obviously quite inadequate to establish it. I may point out, 
however, that the blood in which the encysted trypanosome and 
the vermicule-like bodies were found, was taken from the heart 
of the fish with a capillary glass tube, and it is quite possible that 
the tube in passing through the walls of the heart may have 
taken up bodies which were not free in the general circulation, 
but contained in the wall of the heart itself. 
* Commonly termed “mononuclear” ; a barbarous etymological compound. The 
adjective “nuclear” means “of or relating to the nucleus”; not “possessing a 
nucleus.” 
