vi ACANTHOCEPHALA SYSTEMATIC 183 



mouth and alimentary canal. If the liver of an infested minnow, 

 Leuciscus phoxinus, be examined, it will be found to contain on 

 its surface numerous spherical or egg-shaped capsules of an orange 

 colour, 2 to 2'5 mm. in length; these contain the larval forms of the 

 parasite. They develop into the adult form when the first host 

 is eaten by a carnivorous fish, but a complication may take place 

 when the larval form is found in Gammarus, as the latter, the first 

 host, may be eaten by a fish (intermediate host) in which the 

 larva does not become mature, and only develops sexual organs 

 when eaten by a carnivorous fish (second host). The larval form 

 is also found in Nemachilus barbatulus, Gobio fluviatilis, and the 

 sticklebacks Gasterosteus aculeatus and G. pungitius. 



E. clavula Duj. is found in Salmo fario, Abramis brama, 

 Cyprinus carpio, Gobius niger, Lepadogaster gouanii, etc.; E. 

 linstowi Ham. in Leuciscus idus, Abramis ballerus, Abramis 

 bipunctatus, and Acipenser huso ; E. lutzii Ham. was found by 

 Dr. Lutz in Brazil in the intestine of Bufo agua ; E. angustatus 

 Eud. occurs in such numbers in the perch, Perca fluviatilis, 

 as to almost occlude the lumen of the intestine, and one out of 

 every three or four fish in certain districts is infested by it. It 

 is also found in the pike, Esox lucius, and the barbel, Barbus 

 vulgaris. The first or larval host of this species is the Isopod 

 Asellus aquaticus. E. moniliformis Brews, is stated to attain 

 maturity in the human intestine. Except for the fact that G. 

 gigas has once been observed in the same place, this is the only 

 human parasite amongst the Acanthocephala. Its normal second 

 hosts are Mus decumanus and Myoxus quercinus, and its first or 

 larval host, the larvae of the beetle Maps mucronata. E. 

 porrigens Hud. is found in considerable numbers in the small 

 intestine of a fin-whale (Balaenoptera sibbaldii), and E. strumosus 

 Hud., in the small intestine of a seal (Phoca vitulina\ and in 

 the body-cavity of the angler fish (Lophius piscatorius). E. acus 

 is common in the whiting, Gadus merlangus. 



Family II. Gigantorhynchidae. Large forms with ringed, 

 flattened, and Taenia-like bodies. The hook-papillae are covered 

 all over with transparent chitinous sheaths with two root-like 

 processes. The proboscis -sheath is muscular and without a 

 lumen. The central nervous system is excentrically placed below 

 the middle of the so-called sheath. The lemnisci are long twisted 

 tubes with a central canal. 



