CH.I] IDEA OF INDIVIDUALITY 23 



diametrically opposed and equally active tendencies 

 can scarcely be called an individual. 



The existence of a species or race, a procession 

 of similar individuals each descended from a previous 

 one, as well as of what we usually call individuals, 

 the separate beings that at any one moment represent 

 the species, leads of necessity to the separation of two 

 distinct kinds of individuality, one belonging to the 

 race and one to the persons that constitute the race. 

 Take as an example Distomum hepaticum, the Liver 

 Fluke (Fig. 1). The eggs of this unpleasant creature, 

 which gives sheep the disease known as liver-rot, 

 are passed out of the host and hatch out into minute 

 embryos that swim about in the film of moisture on 

 the meadow-plants. They cannot develop further 

 unless they fall in with a particular sort of snail : if 

 so, they burrow into its liver, and grow up, not into 

 a new fluke, but into an irregular sort of bladder, 

 the sporocyst] this, from its inner wall, produces a 

 number of new embryos which grow and burst out 

 of their parent as the so-called rediae individuals 

 differing both from the fluke or the sporocyst. These 

 in their turn give rise to a number of little tailed 

 creatures, the cercariae, which migrate out of the 

 snail, pass into a resting stage on blades of grass, 

 and there passively await a browsing sheep. If one 

 by good chance devours them, they hatch out, bore 

 their way into the liver, and grow up again into flukes. 



