REPORT OF THE MALARIA EXPEDITION. 29 
Species 2 : H^emamaha relicto, Grassi and Fcletti. Syn. : Hcemamxba relicta + H. sub- 
pracox + H. subimmacuU/ta, Grassi and Feletti ; Pioteosoma grassi/, Labbc ; 
etc. Parasite of sparrows, larks, etc. 
Species 3 : Hamamceba malari^e, Grassi and Feletti. Syn. : Hamamceba lavcvam, 
Labbe, in part. Parasite of quartan fever of man. 
Species 4 : Hamamaeba v'lvox, Grassi and Feletti. Syn. : H^emamceba laverani, Labbc, 
in part. Parasite of tertian fever of man. 
Geims II. H^emomenas, gen. nov. Syn. : Laverania, in part + Hi-etnamceba, in part, 
Grassi and Feletti. The gametocytes have a special form (crescentic). 
Species : Hamomenas pracox, Grassi and Feletti. Syn. : Hamamceba pracox + H. 
immaculata + Laverania malaria, Grassi and Feletti ; Hamamaeba 
laverani, Labbe, in part ; etc. Several varieties - possibly distinct species. 
Parasite of the irregular, remittent, pernicious or aestivo-autumnal fever of 
man. 
The gametocytes of H. danilewskn are crescentic, but they are still shaped like the 
sporocytes (which are also crescentic) — the shape of both being simply determined by the 
exigencies of space within the corpuscle. There appears, then, to be no sufficient reason for 
separating this species from the others of genus H^ernamoeba, in whicli the gametocytes and 
sporocytes have the same shape. On the other hand, Hamomenas pracox is sharply distinguished 
by the gametocytes having a peculiar form of their own. Much confusion lias been caused by 
the belief of Grassi and Feletti, who first named these organisms witli precision, that the 
gametocytes of H. prcecox are a separate species, akin to H. dani/ewskii -both being placed bv 
them in a separate genus, Laverania. This belief they have now abandoned ; and it therefore 
seems necessary also to abandon the genus Laverania. Several observers recognise more than one 
species in genus H^emomenas — namely, a tertian, a quotidian, and possibly an unpigmented 
quotidian parasite ; but, pending further research, we have accepted only one species — H. preecox. 
The different prevalence of the three human species at different but contiguous spots 
(as at Wilberforce and Tower Hill), is hardly consistent with the idea that they are merely 
interchangeable forms of one species of parasite. 
20. Cause of Occasional Failures in Direct Cultivation. — We iiave noted 
^paragraph 5] that a number of Anopheles fed in test-tubes on cases of haemamoebiasis, and not 
fertilized, failed to show parasites ; while two Anopheles which were fed in the same manner 
but which were previously fertilized, did contain them. In this case the failure may be attributed 
to the fact that the patients contained but few parasites and were taking quinine ; but previously 
one of us, in association with Dr. Daniels, obtained negative results with a considerable number 
of Anopheles fed in test-tubes on two excellent cases of crescents in Calcutta. The Italian 
observers also note similar failures in gnats known to be hospitable to the parasites. What is the 
cause ? 
Grassi attributes it to immunity in certain individual gnats. Tiiis can scarcely be the 
