PODOPLEA ISOKERANDRIA 



71 



cpth 



Echinoderms, Annelids, Molluscs, and Tunicates. Zichomolgns 

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

 ranean, on the gills of large species of 

 the Nudibranch, Doris, while L. alheus 

 is found in the peribranchial cavity and 

 cloaca of various Ascidians. Sahel- 

 liphilus may infect the gills of Annelids 

 such as Sahella, and is connnou at 

 Liverpool. 



Fam. 4. Ergasilidae. — Thersites 

 (Fig. 39) is parasitic on the gills of 

 various fishes, e.fi. 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 Eiver 

 Forth into fresh water. The animal 

 possesses claw-like second antennae by 

 which it clings to its host. 



Similarly characterised by the 

 ,'Ant.8. 



¥iG. 38. — Lichomolgus agilis, 

 X 10. Abd.l, 1st abdoniiiial 

 segment ; cpth, cephalothorax ; 

 Th.l, 1st thoracic segment ; 

 Th.5, 5tli thoracic appendage. 

 (After Canu.) 



--Abcl.h2. 



Fig. 39. — Thersites gasterostei. A, 

 9, X 10; B, (5, X 20. Ahd. 

 1 it 2, Fused 1st and 2ud ab- 

 dominal segments; Ant.l, Ant. 2, 

 1st and 2nd antennae ; e.s, egg- 

 sac ; Th, thoracic appendages. 

 (After Gerstaecker. ) 



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

 Bomolochidae, Chondracanthidae, and Philichthyidae. 



Fam. 5. Bomolochidae. — Bomolochus (Fig. 40), parasitic on 

 the skin of the Sole (Solca) and in the nostrils of Cod (Gadus), 

 is held to be related to the Ergasilidae. Tlie first thoracic limb 

 is remarkably modified. Were it not for the absence of a siphon, 

 it would be hard to separate this family from the Caligidae. 



