470 CLASS ECHINODERMATA. 
We sometimes observe at its extremity, a papilla, or a pore, 
which may be an organ of absorption, but it is also certain 
that the animal, when plunged in water, swells in every part, 
and absorbs the liquid through its entire surface, where, it 
has been thought, a net-work of absorbent vessels was ob- 
servable. In the interior, no other part is seen comparable 
to intestines, except two ceca, but little prolonged, attached 
to the base of its prominence. It is tubiform, and on each 
side a vessel extends over its entire length. M. de Blainville 
considers as a nervous system, a filament which stretches 
along the inferior face, but neither M. Rudolphi, nor M. 
Cloquet, will have this to be the case. Certain species have 
a distinct oviduct. In others, the eggs are extended in the 
cellular substance, or the parenchyma of the body. The 
males have a small bladder at the end of the tail, and internal 
vesicule seminales, very distinct. It is probable that they 
fecundate their eggs after they are laid. 
These worms attach themselves to the intestines by means 
of their proboscis, and frequently pierce them. Accordingly 
individuals are to be found in the thickness of the tunics, 
and even in the abdomen, adhering to the intestines in- 
ternally. 
The largest species, Echinorhyncus gigas, Gm., Goetze. 
1—6. Encyc. xxxvii. 2—7, inhabits in abundance the in- 
testines of the hog and wild boar, where the females some- 
times arrive to the length of fifteen inches. 
Certain species, besides the hooks of their proboscis, are 
armed with the like in some other part of their body. 
H#RUwCA, Gm., 
Do not differ from echinorhyncus, except that their pro- 
minence is reduced to a single crown of spines, terminated 
by double hooks. 
One is known which frequents the liver of rats, Heruca 
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