264 SCIENCE PROGRESS 



tozoa — namely, occurrence in the leucocytes— is not to be mini- 

 mised or overlooked, and the genus Leucocytozoon should be 

 retained for these parasites. 



Again, the asexual multiplication or schizogony of the 

 Leucocytozoa of mammals is somewhat specialised. It occurs in 

 a tissue-cell of some internal organ, such as a cell of the liver 

 (L. muris, fig. 4, a), a cell of the lung {L. funambuli, L. leporis), 

 a cell of the bone marrow (L. musculi, fig. 4, c). Schizogony of 

 the parasites of red blood corpuscles most often takes place 

 within the red blood cells themselves, and only rarely in tissue- 

 cells (spleen, liver, etc.). 



However, as the structure and life-history of avian 

 Leucocytozoa are still subjects of controversy, and as the name 

 Leucocytozoon was first applied to parasites of birds, and 

 Liihe seems to restrict the name thereto, the generic name 

 Leucocytogngarina might be used for the highly specialised 

 parasites of mammalian leucocytes, which have a different 

 habitat from the strict Haemogregarines of red corpuscles. 



In connection with the vexed question of nomenclature, 

 protests regarding the abuse of the rule of priority, etc., have 

 been made by several of the most eminent zoologists of the day. 

 Sir Ray Lankester in 1896, in a discussion at the Zoological 

 Society of London, suggested that an international committee 

 should be formed " to produce an authoritative list of names — 

 once and for all — about which no lawyer-like haggling should 

 hereafter be permitted." Nothing of this kind has yet been 

 done. Boulanger (1908), in expressing disapproval of the strict 

 application of the rule of priority, recalls this statement of 

 Lankester, and also states that "names with which all general 

 zoologists, anatomists, and physiologists are familiar should be 

 respected, should be exempted from the rule in virtue of what 

 may be termed the privilege of prescription." 



1 feel that the Leucocytozoa are well included in this category. 

 The name is well established, it is descriptive and self-explana- 

 tory, and has been used continuously in literature by many able 

 workers. For these reasons, together with those cited before, 

 the name Leucocytozoa should be retained for all protozoal 

 parasites of the leucocytes of vertebrates. 



In conclusion, the Leucocytozoa are minute parasites, having 

 a remarkable habitat, namely, within the leucocytes of the blood. 



