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in a very short space of time become overloaded with tape- 

 worms. If it be further asked how the fish in Mr. Simpson's 

 " find " became so charged with parasites in the larval state, 

 my answer is that the fish either actually swallowed part 

 of a dead or dying water-bird charged with mature ligules, 

 or, what would come to pretty much the same thing in the 

 end, it must have swallowed one or several mature tape- 

 worms which were either discharged by the bird, or were 

 seized whilst still remaining suspended from the avian 

 host when swimming on the water. In either case the 

 swallowing of the mature tapeworms would liberate the 

 ciliated ova or embryophores. From the stomach of the 

 fish the six-hooked embryos .would bore their way through 

 the walls of the viscera, and then, having gained access to 

 the great lateral muscles, they would rest there to undergo 

 those metamorphoses through which all the tapeworms 

 pass prior to their passive and final transfer to the body of 

 the ultimate host. The disease thus produced I have 

 called ligulosis, whilst the flesh of fish so affected may 

 in common language be said to be measled, in the same 

 sense as we employ the term to indicate diseased beef 

 and pork from analogous causes. The term " cestode tuber- 

 culosis " suggested by Leuckart, is not I think sufficiently 

 distinctive ; it is even perhaps misleading. 



One of the reasons why many intelligent observers 

 practically deny the powers of entozoal parasites to 

 produce epizooty amongst fishes lies in the circumstance 

 that they do not often find heaps of dead fish lying on 

 the surface of open waters. They forget how soon, in the 

 struggle for existence, the weaker members of a shoal are 

 cut off by the numerous enemies that prey upon them, 

 whether these be sharks, or porpoises and dolphins, or 

 again, fish-eating birds. Another circumstance which I am 



