Ill 



PODOI'LEA ISOKERANDRIA 



Cfth 



,-Th.i. 



Echinoderms, Annelids, Molluscs, and Tunicates. Lichomolgus 

 agilis (Fig. 38) occurs in the North Sea, Atlantic, and Mediter- 

 ranean, on the gills of large species of 

 the Nudibrauch, Doris, while L. aliens 

 is found in the peribranchial cavity and 

 cloaca of various Ascidians. Sabel- 

 lipliilus may infect the gills of Annelids 

 such as Sabella, and is common at 

 Liverpool. 



Fam. 4. Ergasilidae. - - Thersites 

 (Fig. 39) is parasitic on the gills of 

 various fishes, e.g. T. gasterostei, which 

 is common on Gasterosteus aculeatus 

 on the French and North Sea coasts, 

 and may even be found on specimens 

 of the fish that have run up the River 

 Forth into fresh water. The animal 

 possesses claw-like second antennae by 

 which it clings to its host. 



Similarly characterised by the 



,-AnLZ. 



FIG. 38. 



x 10. AM.l, 1st abdominal 

 segment ; cpth, eephalothorax ; 

 Th. 1, 1st thoracic segment ; 

 Th.5, 5th thoracic appendage. 

 (After Canu.) 



FIG. 39. Thernit.es gasterostei. A, 

 9, x 10; B, 6, x -o. AM. 

 1 <t- J, Fused 1st and '2nd ab- 

 dominal segments; Ant./, Ant.2, 

 1st and 2nd antennae ; . 

 sac ; Tit, thoracic append.! 

 (After (lerstarcker. ) 



6 



absence of a siphon are three other families of fish-parasites, tin- 

 Bomolochidae, Chondracanthidae, :uid Philichthyidae. 



Fam. 5. Bomolochidae. Bomoltx-lmx fKig. 40), parasitic on 

 the skin of the Sole (Soled) and in the nostrils <>i' <',M! (Gadus), 

 is held to be related to the Ergasilidac. Tin- lirst thoracic limb 

 is remarkably moditied. AVere it not for ihc absence 'f a si 

 it would be hard to separate this family from the Caligula.-. 



