CONCLUSION 183 



and become complete tape-worms to continue the bud- 

 ding-process as before. 



A drawing is shown of the various stages of develop- 

 ment whereby this creature secures its continuance in 

 Hfe at our expense. The long odds against it are made 

 up for by its extreme fecundity, as in the case of the 

 Uverfluke, each " bud," of which there may be 1,200, 

 containing some thousands of eggs. (See Plate 43.) 



Parasitism has always been going on through the ages, 

 and we are only just beginning, as it were, to feel our 

 feet in the matter. Its range is quite universal and its 

 ramifications so endless that I cannot attempt anything 

 but a general assertion here. The study of parasitism 

 and that of evolution should be braced together ; in fact 

 they will coalesce of themselves without any help from 

 us. When the early naturahsts found, say, ova, larvae 

 or embryos of hitherto unknown forms of life established 

 within the bodies of worms, fishes, birds or mammals 

 quite unaccountably, they propounded the theory of 

 spontaneous generation, somewhat in the same way in 

 which it was at one time believed that showers of frogs 

 came down in a thunder-storm. This idea is now con- 

 sidered to be exploded, although I think it is a dangerous 

 thing to be dogmatic, particularly in regard to natural 

 history, seeing that so many arrangements, classifications 

 and settled convictions have been turned upside down 

 in the past. We have, however, at least traced out the 

 real origins of parasites then thought to be actually brought 

 into being by the host in question. 



For instance, we human beings, dreadful as it may 

 sound, have to our name no less than 120 different species 

 of parasites, including nematoid, cystose and intestinal 

 tapeworms and flukes ; acarid mites ; Crustacea ; dip- 

 terous, suctorial and mallophagous insects ; most of them 

 fortunately of rare occurrence, but which would certainly 

 develop a very absorbing interest in our personal affairs 

 if we did not take stern measures to keep them at arms' 



