406 



HIRUDTNEA 



CHAP. 



Fam. 1. Ichthyo'bdellidae. Body formed of two regions, 

 narrower anterior portion and a wider " abdomen," both anterioi 

 and posterior suckers distinct from the body. 



These leeches are parasites of fishes and of some other 

 animals such as tortoises. The family contains a number of 

 genera. Branchellion (Fig. 204) has a series of 

 leaf-like branchiae on both sides ; in Cystibranehvs 

 the respiratory organs are reduced to a series of 

 round vesicles. The latter genus occurs in Europe 

 and North America, and is parasitic upon marine 

 and fresh-water fishes. Piscicola is a common 

 leech which confines its attacks to the inhabitants 

 of fresh water. Pontdbdella (Fig. 210) is marine, 

 and affects rays and sharks : the best known 

 species, P. muricata, is usually of a green colour. 

 To the family Ichthyobdellidae also belongs 

 the large Chilian leech Macrobdella valdiviana, 

 of which there is or are also species in North 

 America. Philippi's figure of this leech 1 shows 

 the distinct neck ; and as it has no jaws, it 

 should be referred to the present family. It 

 has got an undue reputation for size, 2^- feet 2 

 having been assigned to it. As a matter of fact 

 Philippi's illustration depicts an Annelid of about 

 7 inches in length, with a greatest diameter of 

 about an inch. But doubtless when extended in 

 walking it would be longer- 1^ feet, Philippi 

 thinks. It has no eyes, a failing which is not 

 unusual anions the leeches. 



Fam. 2. Glossiphoniidae. Anterior sucker 

 fused with the body, posterior sucker distinct. 

 No cocoon. 



SEES 



Fig. 210. Pontob- 

 della muricata. 

 x 1. (After 



Bourne.) 



The members of this family all inhabit fresh 

 water ; they have the habit of depositing the 

 eggs separately, which are then fixed to the 

 ventral surface of the body, and the young when hatched are 



1 Zeitschr. f. die gesammt. Natumviss. vi. 1872, p. 422. 



2 But Pennant in his British Zoology has referred to a leech which is even 

 larger. Upon the huge Basking shark (Selache) the fishermen sometimes observe a 

 leech, which invariably drops off when the fish is brought to the surface, " of a 

 reddish colour and about 2 feet in length " ; this may be a Pontobdella. 



i 



