204 Introduction to Aiiinial Morphology. 



under its abdomen for a while. HiEmenteria has a mouth in 

 front, not in the middle, of the sucker, in a protrusible pro- 

 boscis ; both genital openings are on a common wart ; the 

 glands about the neck pour out an irritating secretion, which 

 cause urticaria in the human subject. Piscicola has a linear 

 body with wide anterior genital openings, and is not capable 

 of rolling itself up. 6. Hirudinidse — hermaphrodite ; nar- 

 rowed in front and behind ; four or five rings on each meta- 

 mere ; an anterior sucker present ; pharynx slightly protru- 

 sible, with three toothed jaws ; anus over the hinder sucker. 

 Pontobdella has six eyes, and both suckers are on narrowed 

 ends ; the body warted, not ringed ; they are ecto-parasitic 

 on Fishes. Branchellion has, on each edge, twenty-six leaf- 

 like processes ; they are not ringed, and have 4-8 eyes ; living 

 on the gills of the Turbot and Torpedo, &c. Ichthyobdella 

 is elongated, obsoletely ribbed, with 4-8 ocelli and sub- 

 elliptic suckers. Haemopsis has ten eyes and jaws as 

 hardened folds of the pharynx. These do much mischief, as, 

 when young, they are taken in by cattle with the water which 

 they drink, and attach themselves to the pharynx, and even 

 may enter the wind-pipe. Trochetia has toothless jaws, and 

 genital openings between the 32-3 and 37-8 rings. Aula- 

 costomum (Horse-leeches) are cylindrical, with the hinder 

 lip of sucker obliterated ; caeca small, or none ; intestine 

 wide ; anus large ; genital openings in males between 24-5 

 rings, in females 29-30. Hirudo has the first disc ringed, 

 not separated by a constriction from the flattened body ; eyes 

 10; jaws 3, semilunar, with 30-100 teeth, and 100 rings on 

 the body. H. medicinalis, the German leech, is dark green, 

 with black spots below. H. officinalis, the Hungarian leech, 

 is olive green, without spots below ; each jaw has 70-90 teeth 

 each, with two roots. The sex-openings are as in Aulacosto- 

 mum. They take three years to become sexually mature, and 

 live 18-20 years. The cocoons are laid in summer and 

 winter, and the young embryo begins to creep in 4-6 weeks. 

 A few retain the cocoons attached to their bodies, thus ap- 

 pearing viviparous. 



The thirst for blood in leeches can be increased by putting 

 them in a mixture of wine and water, or one part of vinegar 



