PAKENCHYMATA. 475 



ORDER II. 



PARENCHYMATA. 



THE second order of the Entozoa comprises those species in which the 

 body is filled with a cellular substance or even with a conti- 

 nuous parenchyma, the only alimentary organ it contains being 

 ramified canals, which distribute nourishment to its different 

 points, and wlu'ch, in most of them, originate from suckers visible externally. 

 The ovaries are also enveloped in this parenchyma or that cellulosity. There 

 is no abdominal cavity, or intestine properly so called ; the anus is wanting, 

 and if we except some equivocal vestiges in the first families, there is nothing 

 to be found which bears a resemblance to nerves. 

 We may divide this order into four families. 



FAMILY I. 



ACANTHOCEPHALA. 



THE Parenchymata of this family attach themselves to the intestines by a 

 prominence armed with recurved spines, which also appears to act as a pro- 

 boscis. They form the single genus 



ECHINORHYNCHUS, Gmelin, 



Where the body is round, sometimes elongated, and sometimes in the form of 

 a sac, provided anteriorly with a prominence in the form of a proboscis armed, 

 with little hooks bent posteriorly, and susceptible of being retracted or pro- 

 truded by the action of particular muscles. At its extremity we sometimes 

 observe a papilla or pore which may be an organ of absorption, but it is certain 

 that if the animal be plunged inlo water it becomes universally distended, and 

 absorbs that h'quid through the whole surface, on which it is thought we can 

 discover a network of absorbent vessels. No other parts that can be compared 

 to intestines are visible internally than two slightly elongated caeca attached to 

 the base of the tubiform prominence ; a vessel extends throughout its length 

 on each side. A thread that runs along the inferior face of the animal is con- 

 sidered by M. de Blainville as its nervous system ; but neither Rudolphi nor 

 Cloquet coincide with him. Certain species have a distinct oviduct; in others 

 the ova are disseminated throughout the cellulosity or parenchyma of the body. 

 The males are provided with a little bladder at the end of the tail, and very 

 distinct internal vesiculae seminales. We may believe that they fecundate the 

 ova after they are extruded. 



