342 THE EVOLUTION OF LIFE. 



lower order. So long, too, as we leave out all mortaKty but 

 that which, by carrying off the least perfect members of eacli 

 species, leaves the most perfect members to continue the 

 species ; we see some compensating benefit reached through 

 the suffering inflicted. But what shall we say on finding 

 innumerable cases in which the suffering inflicted brings no 

 compensating benefit ? What shall we say when we see the 

 inferior destroying the superior ? What shall we say on 

 discovering elaborate appliances for securing the prosperity 

 of organisms incapable of feeling, at the expense of misery 

 to organisms capable of happiness ? 



Of the animal kingdom as a whole, more than half the 

 species are parasites. '' The nmnber of these parasites,'^ 

 says Prof. Owen, " may be conceived when it is stated that 

 almost every known animal has its peculiar species, and 

 generally more than one, sometimes as many as, or even 

 more kinds than, infest the human body.'^ Passing over the 

 evils thus inflicted on animals of inferior dignity, let us limit 

 ourselves to the case of man. The Botlirioce^phalus latus 

 and the Tcenia solium, are two kinds of tape- worm, which 

 flourish in the human intestines ; producing great constitu- 

 tional disturbances, sometimes ending in insanity ; and from 

 the germs of the Tcenia, when carried into other parts of the 

 body, arise certain partially-developed forms known as Cysti- 

 cerci, Echinococci, and Ccenuri, which cause disorganization 

 more or less extensive in the brain, the lungs, the liver, 

 the heart, the eye, &c., often ending fatally after long- 

 continued suffering. Five other parasites, belonging to 

 a different class, are found in the viscera of man — the 

 Trtchocephalus, the Oxyuris, the Strongylus (two species), 

 the Ancylostomum, and the Ascaris ; which, beyond that 

 defect of nutrition which they necessarily cause, sometimea 

 induce certain irritations that lead to complete demoraliza- 

 tion. Of another class of entozoa, belonging to the sub- 

 division Trematoda, there are five kinds found in differert 

 organs of the human body — the liver and gall ducts, the 



