vi ACANTHOCEPHALA SYSTEMATIC I 8 5 



nuclei, which remain in the embryonic state and do not break 

 up into numerous nuclei as in other forms. The musculature is 

 but little developed and the longitudinal sheath hardly exists. The 

 proboscis-sheath consists of a simple muscular layer, and the short 

 proboscis has few hooks an<J presents an embryonic appearance. 



The sexually-mature form lives in the carp, Cyprinus carpio ; 

 the larval form is found, according to Villot, 1 encysted in the 

 fat bodies of the larva of Sialis lutaria, one of the Neuroptera, 

 and in the alimentary canal of the leech Nephelis octocula, and 

 successful experiments have been made in infecting some species 

 of the water snail Limnaea. N. agilis occurs in fifugil auratus 

 and M. cephalus. 



Family IV. Arhynchidae. Short forms with the body 

 divided into three well-marked regions head, collar, and trunk. 

 The head is pitted, the collar smooth, and the trunk wrinkled, 

 not annulated, in spirit specimens. There is no eversible intro- 

 vert, and no introvert sheath and no hooks. The sub-cuticle 

 and the lemnisci have a few giant nuclei, and the lemnisci are 

 long and coiled. 2 



This family resembles the Gigantorhynchidae in the length 

 and curvature of its lemnisci, and the Neorhynchidae in the 

 persistence of the embryonic condition of the nuclei in the sub- 

 cuticJe and the lemnisci; but in the shape of the body, its 

 division into three well-marked regions, the absence of eversible 

 proboscis, proboscis sheath, and hooks it stands alone, though it is 

 nearer to the Neorhynchidae than to either of the other families. 



The single species Arhynchus hemignathi was found attached 

 to the skin around the anus of a Sandwich Island bird, Hemi- 

 gnathus proceros. The bird is a member of a family Drepani- 

 didae, which is entirely confined to the Sandwich Island group. 

 Professor Newton tells me that it is probable that "the " food of 

 Hemignathus consists entirely of insects which it finds in or 

 under the bark of trees," hence it is probable that the second 

 host of this parasite, if such exists, must be looked for amongst 

 the Insecta. 



1 Zool. Anz, vol. viii. 1885, p. 19. 

 8 Shipley, Quart. J. Micr. Sci. vol. xxxix. 1896. 



