150 THE HAUNTS OF LIFE 



skin of the minnow ; the others perish. The 

 Glochidia are somehow attuned to answer back 

 to minnow, and if we have some in a soup-plate 

 they become greatly excited if a little piece of 

 dead minnow is dropped into their midst. In 

 some North American fresh-water mussels it is 

 to one kind of fish, and to that alone, that the 

 larvae respond. So subtly interlaced are the 

 threads of the web of life. But returning to our 

 own rivers and ponds, we find that the Glochidia 

 remain for a considerable time on their bearer, 

 the minnow, burrowing a little way into the 

 flesh, and undergoing a great change in the 

 architecture of their body. When the great 

 change or metamorphosis is accomplished, they 

 drop off into the mud and start an independent 

 life as young fresh-water mussels, often far from 

 the place where they were born. We under- 

 stand then that the fresh-water mussel cannot 

 continue its race unless there is this strange 

 linkage with a minnow. 



And just as the mussel is linked to a fish, so 

 there is a fish which is linked to the mussel. 

 For the Bitterling, Rhodeus amarus, which 

 lives in some continental rivers, has a long egg- 

 laying tube with which the eggs are actually 

 injected into the fresh- water mussel. The eggs 



