BALANTIDIUM HAUGHWOUTI, NEW SPECIES, PARASIT- 
IC IN THE INTESTINAL TRACT OF AMPULLARIA 
SPECIES, A MORPHOLOGICAL STUDY 
WITH REMARKS ON THE RELATION BETWEEN THE MEGANUCLEUS 
AND THE MICRONUCLEUS 1 
By Walfrido de Leon 
Instructor, Department of Pathology and Bacteriology, College of Medicine 
and Surgery, University of the Philippines 
ONE PLATE AND FIVE TEXT FIGURES 
INTRODUCTION 
This is a study of the structures and the characters of what 
appears to be a new species of Balantidium found parasitic 
in the intestinal tract of a fresh-water snail, Ampullaria sp. 
The parasites were first seen by Prof. Frank G. Haughwout in 
the original host found in the pond on the ground of the Bureau 
of Science, Manila. 
The host, Ampullaria, is a very common inhabitant of. fresh 
waters in the Philippine Islands. It thrives luxuriantly about 
the banks and the bottoms of shallow rivers and ponds. It 
is known in the vernacular as “cohol” and is much used as a 
food by the Filipinos. 
The discovery of this species is of some systematic interest 
in that it forms an addition to the species of Balantidium that 
have been found infesting invertebrate hosts. 
THE GENUS BALANTIDIUM 
The genus Balantidium was founded by Claparede and Lach- 
man.(lO) It consists of heterotrichous ciliates, free-swimming 
or histozoic, oval in shape, slightly truncated anteriorly and 
more rounded posteriorly. A small triangular excavation, an- 
teriorly, forms the peristome at the bottom of which opens the 
cytostome which leads backward into a fairly well-developed 
1 From the department of parasitology. Submitted in partial fulfill- 
ment of the requirements for the degree of Doctor of Tropical Medicine, 
Graduate School of Tropical Medicine and Public Health, College of 
Medicine and Surgery, University of the Philippines. 
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