PHYLUM ANNELIDA 



2 39 



skin. Waste products are extracted from the blood and ccelomic 

 fluid by seventeen pairs of nephridia (Fig. 170, 10) which re- 

 semble those of the earthworm (Fig. 

 153, neph), but frequently lack the 

 internal opening. 



Leeches are hermaphroditic, but the 

 eggs of one animal are fertilized by 

 spermatozoa from another leech. The 

 spermatozoa arise in the nine pairs 

 of segmentally arranged testes (Fig. 

 170, 12); they pass into the vas 

 deferens (13), then into a convoluted 

 tube called the epididymus (14), where 

 they are fastened into bundles called 

 spermatophores, and are finally de- 

 posited within the body of another 

 leech by means of the muscular penis. 

 The eggs arise in the ovaries of which 

 there is a single pair (16) ; they pass 

 into the oviducts, then into the 

 uterus {17), and finally out through 

 the genital pore ventrally situated in 

 segment XL Copulation and the 

 formation of a cocoon are similar to 

 these processes in the earthworm 

 (p. 226). 



Many leeches have jaws resembling 

 those of Hirudo, for example Hcemopis 



and Macrobdella, but others have a slender protrusible proboscis 

 in place of jaws. Clepsine (Fig. 171) belongs to the latter 

 type; it feeds chiefly on fish and snails. Ichthyobdella and 

 Pontobdella (Fig. 171) are marine jawless leeches which are 

 parasitic on fish. 



B 



Fig. 171. — Two leeches. 

 A, Pontobdella. B, Clepsine. 

 (From Parker and Haswell. 

 A, after Bourne ; B, after 

 Cuvier.) 



