PODOPLEA ISOKERANDRIA 



75 



exterior. Feroderma cylindricum bores similarly into the flesh 

 of the Sardine, and where it is common, inflicts considerable 

 damage. The males of these curious animals are of more 

 normal structure (Fig. 45). Claus^ states that fertilisation 

 takes place when both sexes are free-swimming, and of a more 

 or less similar stmcture, and that subsequently the female 



MX2: 



Fig. 45. — Lernaea hranchialis, Fio. 46. — Achtheres percarum. A, 9 , x 4 ; B, 



(J, X 10. Ant.l, Ants, 1st 

 and 2nd antennae ; Br, brain ; 

 e, eye ; g, stomach ; t, testis ; 

 vd, vas deferens ; ves. sem, 

 vesicula seminalis. (After 

 Clans.) 



(5 , X 4. Ant.S, 2nd antenna ; g, stomach ; 

 Mx.Z, 2nd maxilla; Mxp, maxillipede ; 

 ovary ; ovd, oviduct. (After Gerstaecker. ] 



becomes fixed to her host and degenerates into the shapeless 

 mass shown in Fig. 44. 



Fam. 12. Lernaeopodidae. — This family may be illustrated 

 by the common gill-parasite of Perch and Trout, known as 

 Achtheres percarum. The female (Fig. 46), which is much larger 

 than the male, and is not clearly segmented, is attached to the 

 host by means of the maxillipedes, which are fused distally into 

 a pad armed with chitinous hooks. In the male the maxillipedes 



' Olauo, Schriften d. Gesellsch. Marburg. Suppl. 1868. 



