STONE-TURNING 



573 



FRESH-WATER LEECHES 



One turned upon its back 



to show the suckers. 



(Natural size.) 



has a " creeper " or two upon it. and 

 several Ephemerid or May-fly lar\-;t. 

 The stout " creepers " are. as a rule, less 



than an inch in 

 length and 

 readily detected 

 while trying to 



t,^^ waggle quickly 



^» out of sight ; but 



we may haye to 

 ^^^ look two' or 



■^^^ three times for 



the Ephemerid 

 larvae, as they 

 often remain 

 squat and still ; 

 and so perfectly 

 do their colours 

 blend with the 

 green and brown hues of the wet stone, 

 that one is apt, at a first glance, to pass 

 them over unnoticed. 



The body of the " creeper " is divided 

 up like that of a Centipede ; but the head 

 is big and flat, and almost as broad as 

 the first three body segments, which have 

 flat horny shields like half moons, and 

 which are very much wider than the 

 others behind. The eyes are prominent, 

 and the head has two long sensory feelers. 

 A similar pair of thread-hke tactile pro- 

 cesses project from the end of the body. 

 The " creeper " swims well ; its three 



pairs of legs are 

 noticeably fringed 

 w i t h swimming 

 hairs. Put a 

 " creeper " into 

 water and you 

 will see little 

 bunches of fine 

 filaments on the 

 sides of its body. 

 The Caddis-worm 

 and the May-fly 

 larva have, in the 

 same position, somewhat similar struc- 

 tures. Breathing organs these are, con- 

 nected to the air-tubes which ramify 

 throughout every part of the body, con- 

 veying fresh oxygen to the tissues and 

 taking away the impure gases. 



Ah insects breathe by air-tubes, or 



tracheae, as they are technically termed ; 



but in the terrestrial forms the air-tubes 



are in direct communication with the 



73 



FRESH-WATER SHRIMPS 

 (Natural size,) 



outside air through little openings at 

 the sides of the body. The contained air 

 gives these fine, thread-like, respiratory 

 tubes a beautiful silvery ai)pearance. 

 ^^ Perla, the Stone-fly, which the 

 "creeper " ultimately becomes, does not 

 differ greatly in appearance from the 

 Caddis insect except that it is larger, 

 and closes its wings flat upon the back 

 when about to rest, whereas the Caddis- 

 fly holds them pressed against its sides. 



VARIOUS FORMS OF SPONGE SPICULES. 

 (Magnified forty diameters.) 



It is a queer trout that will not rise to a 

 " creeper." 



And what is the tough, o\-al, fleshy 

 thing stin sticking to the wet stone ? A 

 fresh-water Leech. Such an odd way it 

 moves, fixing first one end, and then 

 looping itself up to fasten the other end 

 close behind where it fixed the first one. 

 It stretches out like a worm, which indeed 

 it is, a kind with two suckers, one at 

 either end of the body. 



A closer inspection of the wet surface 

 of the stone re\-eals a number of tiny 

 objects, hke very young caterpillars, 

 shding along and bending their bodies 

 into so many letters U. They are the 

 lar\-al stages of a common midge. Unless 

 it be the small amphibious (Limnaea) 

 Snail, which we see in clusters upon almost 

 every stone, there is no more familiar 

 denizen of our running waters than the 

 little fresh-water shrimj). Gammarus ; 

 the creature with the compressed, cres- 



