150 LECTURE XIII. 



segment is called the abdomen, and in it the ovaria are developed. 

 You will not unfrequently find adhering to the eye of the sprat an 

 Epizoon or Lernaea *, which is a nearly allied species of the same 

 genus (^Penicidiis), as the specimen figured and described by Nord- 

 man {fig. 78.), which infests the boar-fish {Zeus cqier). In the 

 Peniculus fistula the head {fig- 79, /i) is oval, and notched anteriorly, 

 each division being armed with an inwardly bent hook, or rudimental 

 jaw. The mouth («) is immediately beneath these, in the form of a 

 circular orifice, supported by a short cartilaginous tube. At the 

 posterior contracted part of the head are two pairs of short, oval, 

 flattened processes : a constriction or neck separates them from the 

 thorax (<), at the commencement of which there is a third pair of 

 similar rudiments of locomotive appendages. The thorax is round, 

 and separated by a constriction from the abdomen {ab), a fourth 

 pair of appendages being developed from the interspace. The 

 alimentary canal {d, d) is much contracted in the neck and thorax, 

 but expands in the abdomen into a moderately wide and uniform 

 intestine, which again slightly contracts to terminate at the hinder 

 extremity. The alimentary canal has the same simple straight course 

 in other species of Epizoa. One cannot be surprised at this corre- 

 sjDondence with its general condition in the cavitary Entozoa, when 

 the similarity of their easily assimilable nutriment is remembered. It 

 is, however, complicated in the Epizoa, with a conglomerate or mi- 

 nutely-lobed glandular mass, developed from nearly the whole extent 

 of the abdominal tract of the intestine, and which may fulfil the 

 function of a liver. 



In some species which attach themselves to the gills and the like 

 favourable positions for an abundant suj^ply of the most nutritious 

 fluid, the body is frequently deformed, as it were, by excessive 

 growth, and ctecal productions from the simple straight intestine are 

 continued into the prolongations of the thoracic or abdominal walls. 

 The Nicothoet, a small parasite of the gills of the lobster, is an 

 example of this condition of the digestive organ. The first segment 

 of the body is produced into two lateral symmetrical wing-shaped 

 lobes, each four times the length of the segment to which they are 

 attached, and they contain corresjDonding csecal prolongations of the 

 straight intestine. 



In the species of Lernaea exhibited (JPenictdiis fistula), the abdomen 

 contains, in addition to the alimentary canal, two slender tubes (o, o), 

 commencing by blind extremities near the anterior part of the dilated 

 intestine, and continuing with a slightly wavy course to terminate at 

 the two apertures, to which the ovisacs (f) are attached. 



* No. 287. A. 



f Audouin and Edwards, Crnstacees, 1829, 8vo. p. 1. 



