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E. A. MINCHIN AND H. M. WOODCOCK. 
to the condition in which we found L. ziemanni in some of 
our owls. The L. caulleryi phase, on the other hand, 
appears to represent an older condition of the parasites — 
probably a much older infection — in which the gametocytes 
are quite mature, it may be, over-ripe. In such a case one 
may suppose that many of those which do not succeed in 
passing into the alternate host at length die off. It is not 
unlikely, we suggest tentatively, that others are able to 
undergo some parthenogenetic development and give rise later 
to a fresh succession of gametocytes in the blood. In this 
manner the reappearance of the parasites after an interval 
could be readily explained. 
We may conclude our remarks on Leucocytozoon 
ziemanni by giving extracts from our notes relating to one 
or two interesting observations on the gametes, which we 
were fortunate enough to find in living preparations. The 
male gametes were first detected by the movements of the 
corpuscles which they caused. They appeared as very 
slender, spirocliaete-like bodies, exceedingly active, perform- 
ing twisting movements and travelling at a fair pace; they 
were rather longer than a red corpuscle and capable- of 
jerking the corpuscles about. Three or four of these 
delicate elements were seen in an area rather larger 
than a field of the microscope. In another field an active 
male gamete was found and also a rounded-off female 
individual ; the latter was quite spherical and had ruptured 
its host-cell, the remains of which, together with the nucleus, 
were still attached to one side of the parasite. The male 
gamete was at first some little distance from the female 
element ; it travelled fairly fast, and in keeping it in view 
the female individual was sometimes quite out of the field (of 
the oil-immersion lens), and then would be brought in again, 
i.e. the microgamete was sometimes nearer to, at other times 
farther from, the female. Once the male was seen to travel 
in a straight line rapidly towards the female till it nearly 
reached it; but then it turned off to one side again. After 
moving about a little longer, however, the microgamete at 
