104 EVOLUTION 



of parasites are among the very strangest 

 disentanglements of the web of life, but into 

 the stories of these adventures in search of 

 mischief we cannot enter here: enough if we 

 note the stupendous rate of multiplication 

 e Inany chances aainst 



>Lhe piioper h o st ^ -&rfi op i? s t n n tJ v TP c ^ * thus 

 the summon tape- worm ^of man has, been 

 *- ; calculated i to produce ei 



*- ; 

 l 



itstwo years' 



It is an interesting inquiry whether the 

 large numbers of so-called species of thread- 

 worms, tape-worms and other parasites, are 

 not, in many cases at least, mere modifica- 

 tion forms, whose diagnostic characters are 

 directly induced by the peculiarities of 

 their respective hosts. The question is, of 

 course, one for the experimental observer. 



Again, even parasitism must not be viewed 

 too pessimistically. Tt is n after 



t.n VM1 Ujg host, f\r 



|n r|^^|orqtp its Kte too seriously: 

 moreover the jio^t. bppornegf more or less 

 ^> ]t. s wonted guests, and probably 



pojsons which many parasites have been 

 shown to excrete. The rapid disasterjkich 

 Vring aTior^, PTTPS rpjh.gr 



when intrQduced_into SQTT|^ new ^nd nna.n-. 

 customedjiost ; as probably, in tjie case _pf 

 sleeping sickness. 



