A. Porter 
41 
fine, curved, radiating canaliculi, opening into a central space. The 
excretory products are faintly reddish in colour. The presence of a 
contractile vacuole is uncommon in parasitic Amoebae. 
The nucleus is poor in chromatin. A nucleolus is present. 
A. chironomi is highly sensitive to the degree of concentration of 
the medium in which it lives. Very slight increase in density causes 
the organism to encyst. 
Encystment occurs in the rectum of the host, and the cysts are 
voided with the faeces. The cysts are from 12//, to 20//. long and from 
9// broad. The process of encystment is rapid. 
The method of cross-infection of the host is probably a “ casual ” 
one, viz. by the mouth. 
REFERENCES. 
Butschli, 0. (1878). Amoeba blattae. Zeitschr. f. wiss. Zoologie, xxx. p. 273. 
Miall, L. C. and Hammond, A. R. (1900). The structure and life history of the 
Harlequin Fly ( Chironomus ). 196 pp. Clarendon Press, Oxford. 
Schubotz, H. (1905). Beitrage zur Kenntnis der Amoeba blattae (Butschli) und 
Amoeba proteus (Pall.). Arch. f. Protistenlcunde, vi. pp. 1—46, 2 pis. 
