150 Transactions of the Societi/. 



forms. He also thought there was a trypanosome form in the bird, 

 but I have failed to find anything at all like a trypanosome. The 

 dark plasma-staining seems to indicate that the forms in the blood 

 are macrogametes, and occasionally I have found forms with very 

 delicate plasma-staining which might perhaps be regarded as micro- 

 gametes. I could not find the division-forms described by Laveran. 

 The earlier observers of this parasite — Danilewsky and Ziemann — 

 believed that the host-cell was a leucocyte, but Laveran has shown 

 that it is an erythrocyte. 



There is an analogy between the curious enlargement of the 

 host-cell and the enlargement and de-htemoglobinization of the 

 erythrocytes of snakes, containing one of the varieties of htemo- 

 gregarines which I have mentioned to you before. I have found 

 these parasites in two lairds only, both of which are new as hosts. 



Leucocytozoa found in the Blood of Birds. 



Habitat 



Scaup's Duck — Fuligula marila Europe 



LevaillanVs Francolin — Francolinus levaillcmti Cape Colony 



I am afraid I have given you nothing but scraps ; indeed, 

 spying at these things with the highest power objectives is some- 

 thing like looking at the closed edges of a book you cannot open ; 

 you have had a few of the frayed edges ; but I have every hope 

 that all its pages will be open and clear to us one day. 



In conclusion, there are many things which are yet invisible 

 to the highest microscopic abilities ; there are even things called, 

 in confusion of thought, " ultra -microscopic." Whether such 

 actually exist, I do not know. I do not believe they do, in the 

 exact sense. Think what the Microscope has accomplished since 

 the days of Leuwenhoek, and, at any rate, let us see to it that 

 nothing remains unseen because of our methods, or want of 

 methods ; let us all go on working unceasingly, keeping our faces 

 forward, so that our Society shall continue to be a living, fertilizing 

 stream, and not become converted, by our apathy, into a stagnant 

 pool. 



