76 



CRUSTACEA COPEPODA 



are prehensile, but are not so fused. Besides Achtheres there are 

 other fresh-water forms, e.g. Lernaeofoda salmonea on Salmon, 

 and a number of marine genera. It appears that the larvae fix 

 themselves to their hosts by means of a long glandular thread, 

 whicli proceeds from the middle of the forehead.^ 



Fam. 13. Choniostomatidae." — The members of this family 

 are all parasitic on other Crustacea. The majority live parasiti- 

 cally in the marsupial pouches of female Amphipods, Isopods, 

 Mysidae, and Cumacea, e.g. l^phaeronelkc and Stenochotheres in tlie 



marsupiaof Gammarids ; but Chonio- 

 stoma occurs in the branchial cavity 

 of Hijopolyte, Homoeoscelis is common 

 in the branchial cavity of Dieistylis 

 and l-phinoe, and Asjndoecia on the 

 outside of the body of the Mysid 

 ErytJirtyps. The males and females 

 live together in the same marsupium, 

 l)ut the adult males retain the power 

 of roving about, and do not feed so 

 much as the females, though their 

 mouth - parts are similarly con- 

 structed (Fig. 47). Piepresentatives 

 occur all over the world, but the 

 majority of species known at pre- 

 FiG. 47.— Ventral view of stenocho- gent are from the North Sea, the 



</ieresegfre7Mts(Choniostomatidae), , , . . _, 



most abundant bemsf htenociiotneres 



6 • A, A', 1st and 2nd antennae ; 

 M, mouth ; Mx, 2nd maxilla ; 

 T, 1st thoracic leg. (After Han- 

 sen.) 



egregius, parasitic on the Gammarid 

 Metopa hruzelii, Goes. 



The male bears a median glandu- 

 lar thread on the forehead by which it attaches itself to the 

 females or to the host. Hansen considers that the family is 

 most closely allied to the Lernaeopodidae. 



BEANCH II. BKANCHIURA. 



Fam. Argulidae.^ — We have yet to mention tliis group of 

 fish-parasites, related to the Copepoda, but occupying an isolated 



' Clans, Zcitschr. wiss. Zool. xi., 1861, i). 287. 



- Hansen, "The Choniostoniatidae," Copenhagen. 



^ Glaus, Zeitschr. wiss. Zool. xxv., 1875, ji. 217. 



