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Amoeba Chironomi, Nov. Sp. 
Cross-infection of the Host. 
The method of cross-infection of the larvae of Chironomus is 
probably a casual one, namely, by swallowing the voided cysts of Amoebae 
from infected larvae. I can state that I have seen larvae of Chironomus 
begin to feed on the vegetable tubes of other Chironomi, and that 
voided castings containing cysts occur in these tubes. Casual infection 
by the mouth is now known to be a very common method of trans¬ 
ference of protozoal organisms from host to host, and it is probable that 
such is the case here. 
General Remarks. 
Many parasitic Amoebae, often styled Entamoebae, are known to 
occur in the digestive tracts of Vertebrates. Some Amoebae are also 
known from the alimentary tracts of Invertebrates, but at present 
these are fewer in number. In insects probably the best known 
parasitic Amoeba is that recorded by Biitschli (1878) from the cock¬ 
roach, and named by him Amoeba blattae. Further researches have 
been conducted on this parasite in recent years (see Schubotz (1905) 
and others). An Amoeba (A. sagittae or A. chaetognathi) has, I believe, 
also been recorded by Grassi from the arrow-worm, Sagitta. 
Miall and Hammond (1900) in their excellent account of the 
Harlequin Fly ( Chironomus ) do not refer to the parasitic Amoeba 
described in this paper, though they mention other parasites of 
Chironomus. 
The exact species of Chironomus larvae investigated is difficult to 
determine. The commoner ones are C. dor'salis and C. plumosus. 
Probably the larvae of one of these species yielded the material for 
this research. 
Summary. 
Amoeba chironomi, nov. sp., is distributed through practically the 
entire length of the digestive tract of the larva of Chironomus. 
The body of A. chironomi varies from 15/r to 18/z. in length and 
from 10/r to 12/z. in breadth. The single pseudopodium may reach 15/x 
in length; one pseudopodium only is usually present. 
Ectoplasm and endoplasm are well differentiated. A nucleus and 
a contractile vacuole are present. Food vacuoles are rare. The con¬ 
tractile vacuole resembles an iris diaphragm, consisting of a series of 
