The Infe-history of Trypanosoma equiperdum. 289 
tudinal fission of the trypanosomes, until a vast number of trypanosomes are 
produced and the infection of the blood reaches a first maximum. (See 
chart, p. 290.) 
After such a period has been reached, the number of parasites in the blood 
falls until it may be impossible to detect their presence. But subsequently 
parasites reappear, and a second maximum is reached, and so on. The 
alternations of these maxima and minima in rats during an infection with 
T. gambiense are illustrated in the chart given on p. 290. Inthe case of man, 
trypanosomes by Schaudinn, Prowazek, Minchin, and others, but we have been uniformly 
unable to confirm these observations, and have reached a diametrically opposite con- 
clusion, namely, that in the case of Trypanosoma gambiense, T. equinum, T. lewist, 
T. brucei, and T. equiperdum, chromosomes are not present, and do not exist, at any rate 
during those forms of division which take place in the blood of a mammal infected 
with these trypanosomes. 
[Footnote added April 18, 1908.] 
Minchin, in the ‘Quart. Journ. Micro. Sci.,’ vol. 32, Part II, describes the structure we 
term extra-nuclear centrosome as the kineto-nucleus, and a different structure, a small 
swelling or bead, at the end of the stainable portion of the flagellum, as the blepharoplast 
or centrosome. The reasons for regarding the body we term the extra-nuclear centro- 
some as a centrosome are as follows :— 
The extra-nuclear centrosome appears to be derived from the intra-nuclear centrosome, _ 
and the intra-nuclear centrosome (karyosome nucleolus) appears to be a structure which 
is closely similar in its appearance and behaviour to the undoubted intra-nuclear 
centrosomic, or blepharoplastic, bodies within the nuclei of Euglena, and many protozoa. 
This conception is strengthened by the fact, originally observed by one of the present 
authors in 1894 (Moore, ‘ Internat. Monatschr. f. Anat. Physiol. vol. 11), that the true 
metazoan centrosome is regularly incorporated within the flagellated male gametes 
of these organisms. In such gametes the centrosomes become more or less definitely 
related to the flagella, just as the extra-nuclear centrosome is related to the flagella 
of the trypanosomes. In many metazoan gametes (reptiles) the flagellum abuts directly 
upon the centrosome. In others (some mammals) this is not so, the flagellum ending in 
a small bead corresponding to the blepharoplast of Minchin. In such cases the true 
centrosomes remain quite detached, as in some trypanosomes, for example in 7. lewosz. 
The bead, when it exists on the base of the metazoan flagellum, is not a centrosome, but 
simply an enlargement of the proximal end of the flagellum. For this reason we do not 
regard the blepharoplast of Minchin as equivalent to the blepharoplastic, or centrosomic, 
structures of other cells, but we regard the bead in question as possibly equivalent to the 
swelling at the end of the flagellum found among many metazoan cells and gametes. 
Similarly, we regard the name kineto-nucleus, when applied to what we call the extra-nuclear 
centrosome, as entirely inappropriate. In the first place, in so far as this structure can 
be homologised with any structure known in other cells, it appears, as we have said, to 
have the same relationships as the centrosome. In the second place, it does not appear 
to have any attributes, except the capacity to divide (a capacity which, of course, is 
shared by all centrosomes), in common with what is understood as a nucleus. Minchin 
draws attention to the large size of the extra-nuclear centrosome (kineto-nucleus, 
_ nucleolus blepharoplast) in some trypanosomes, as indicating that this structure is not of 
the nature of a centrosome ; but we are unable to see that the dimensions of this body 
affect the matter in any way, for the undoubted centrosomic or blepharoplastic structures 
of many male plant gametes are similarly large, if not larger. 
