LEECHES. 



49 



In the leech, which is the type of the first and lower 

 order, the body is somewhat flattened and divided into 

 numerous short, indistinctly marked segments, not bear- 

 ing any bristles or appendages. The head is small, with no 

 appendages, bearing five pairs of simple eyes, while each 

 end of the body terminates in a sucker. The mouth is 

 armed internally with three teeth arranged in a triradial 

 manner (Fig. 51, t'), so that the wound made in the flesh of 

 persons to whom the leech is applied consists of three short,^ 

 deep gashes radiating from a common centre. Our com- 

 mon pond leech {Macroidella decora, Figs. 53, 53) is of a 



Fig. 51 Common fish-leech, a, 



natural size ; &, head with two 

 eyes; c, teeth, Gissler, del. 



Fig. 52.— Young Macrohdella de 

 cota. Body unnaturally flat 

 tened. Gissler, del. 



rich deep olive color above, and orange red on the inid^r 

 side. It IS four inches in length. Another common pond 

 leech is Ne^yhelis, of which we have several species. 



The eggs of leeches are laid in sacs, or, as in Clepsine 

 (Fig. 51), the fish-leech, are covered with a transparent 

 fluid substance, which hardens and envelops the eggs. The 

 Clepsme remains over the eggs to protect them until they 

 hatch; and the young fix themselves to the under side of 

 the parent, and are thus borne about until they are fully 

 developed and able to provide for themselves. 



