270 LECTURE Xlll. 



contracted in the neck and thorax, but expands in the abdomen 

 into a moderately wide and ' uniform intestine, which again 

 slightly contracts to terminate by a distinct anus at the hinder 

 extremity. The alimentary canal has the same simple straight 

 course in other species of Elpizoa. One cannot be surprised at this 

 correspondence Avith its general condition in the cavitary Entozoa, 

 when the similarity of their easily assimilable nutriment is remem- 

 bered. The intestine is, however, complicated in the Epizoa with a 

 conglomerate or minutely-lobed adipose mass, which surrounds, like 

 a net-work, nearly the whole extent of the abdominal tract of the 

 intestine in Lerncsa, Lerneocera, and Lamproglena, and which 

 Nordmann supposed, from its gland-like character, might fulfil the 

 function of a liver. 



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

 favourable positions for an abundant supply of the most nutritious 

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

 growth, and cgecal productions from the simple straight intestine are 

 continued into the prolongations of the thoi'acic or abdominal walls. 

 The Nicothoe, a small parasite of the gills of the lobster, is an ex- 

 ample 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 corresponding ceecal prolongations of the straight 

 intestine.* 



In the Peniculus fistula, the abdomen contains, in addition to the 

 alimentary canal, two slender tubes, the ovaria and oviducts (o, 6), 

 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 are attached. These ovisacs 

 (y*) singularly resemble the seed-capsules of certain plants, the Cassia 

 fistula, e. g., being divided into a series of cells or chambers by 

 transverse septa, placed at regular distances. Each cell contains an 

 elliptical or lenticular ovum. 



Two slender white filaments (g g) running almost parallel with, 

 but at a distance from, each other, tlirough the whole length of the 

 under surface of the abdomen, nearer the margins than the middle 

 line, form the chief and most conspicuous part of the nervous system. 



The Epizoa differ from one anotlicr in their mode of adhering to 

 the fish they infest : some stick fast by a suctorial mouth ; others by 

 processes that grow from the head ; but the most common n)cchanism 

 of adhesion in this singular class is a circular sucker, ^^. 116, ?», 



* CCIX. 



