728 , H. M. WOODCOCK. 



6. Note on Leucocytozoon fringillinaecm, n. hv. 



Habitat. — There has been considerable discussion with 

 regard to the exact nature of the host-cell in which these 

 Avian leucocytozoa are parasitic, some authorities stating 

 that it is a leucocyte, while others regard it as an erythro- 

 blast, or else an altered red cell. I have been able to assure 

 myself that in the case of this species the host-cell is 

 undoubtedly a uninucleate leucocyte, and not an inmature 

 red cell or erytlirobiast.^ Alter once carefully comparing 

 them there is little difficulty in distinguishing between these 

 two types of cell. Examples of immature red cells are seen 

 in figs. 22 and 57, and of uninfected uninucleate leucocytes 

 of about the same size, or a little larger, in figs. 23 and 58. 

 The nucleus of the leucocyte is relatively larger than that of 

 the other type of cell, occupying, indeed, most of the body ; 

 moreover, it is nearly always eccentric in position, with the 

 result that the cytoplasm lies chiefly on one side, whereas the 

 nucleus of the erythroblast is central. The appearance of 

 the two nuclei is also different. The latter contains many 

 small chromatic masses ; that of the leucocyte, on the other 

 hand, appears to have a few lai-ge masses, which by the 

 Komanowsky method of staining do not stand out so sharply 

 from the general nuclear substance as in the other case. 

 Further, the cytoplasm of the leucocyte is always distinctly 

 paler than that of the other kind of cell. 



From the immature red cell all transitional stages occur to 

 the ordinary full-sized red blood-corpuscle ; but I have seen no 

 connection whatever between such cells and the others — the 

 uninucleate leucocytes — which are entirely distinct. More- 

 over, in no case have I found the parasites occurring in the 

 former type of cell, but always only in the leucocytes. 

 Wenyon, in his account of L. nu midge (37), figures unin- 

 fected cells belonging to this type of immature red cell, above 



' From the observatious which I have so far been able to make upon 

 L. ziemauui, iii the httle owl, I am strongly inclined to think that 

 the same is true for this parasite also. 



