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system of extremely fine excretory tubules. The tubules 

 join to form larger canals that unite together into one or 

 more main canals (collecting tubes) which open to the 

 exterior by one, two, or many pores. 



The flame-cell is the first portion of an excretory tubule, 

 the slightly dilated part with the blind end. It has delicate 

 protoplasmic processes extending into the parenchyma, a 

 nucleus at the blind end, and a somewhat conical cavity 

 continuous with that of the tubule. At the base of the 

 cavity there is a bunch of cilia which in vibratile action 

 resembles a flickering flame. 



CLASS TREMATODA (FLUKES). 



"What is the general course of development in a Monogenetic 

 Trematode? 



The ectoparasitic Monogenea affect one host only (e.g., 

 a fish or a frog), the development is direct. The eggs are 

 developed outside the parent. The ciliated embryos or 

 larvae are often free-swimming. After a simple meta- 

 morphosis, the adult state is attained. 



Structure and Life-History of Fasciola, syn. Distomum 

 (the Liver-fluke). 



Where is the Liver-fluke ( Fasciola hepatica) found ? Which 

 diseases does it cause ? 



The adult Liver-fluke commonly infests the biie- ducts 

 of the sheep and other herbivorous mammals in many 

 parts of the world, and produces the wasting disease known 

 as " liver rot." In Man it is a rare incidental parasite. 



N. B. When a parasite occurs occasionally in a host 

 which is not its usual or specific host, it is then said 

 to be incidental to that host. 



What is the General Appearance of the Adult Liver-fluke ? 



It is about an inch long, flat and oval, and has at the 



broader " shoulder " end a characteristic blunt triangular 



