42 ZOOLOGY. 



senting the ambulacra, or confined to the middle portion of the ventral 

 surface. The mouth is fringed with branching tentacles capable of being 

 withdrawn ; the vent is at the opposite extremity of the body ; and the entire 

 animal bears a strikins: resemblance to'^' cucumber, whence it is called by 

 sailors the sea-cowcumher^ and one of the genera bears the nai^e of 

 Oucumaria {C. frondosa^ pi. 76, Jig. 85). They are extensively collected 

 about the islands and reefs of the Eastern oceans as a culinary delicacy for 

 the Chinese markets. 



Captain Flinders mentions a Malay fleet of sixty vessels and one thousand 

 men, as funning an expedition to fish for these animals. 



" The object was a certain marine animal called trepang ; of this they 

 gave me two dried specimens, and it proved to be the heche-de-rner or sea- 

 cucumber, which we had first seen on the reefs of the east coast, and ha(i 

 afterwards hauled on shore so plentifully with the seine, especially in Caledon 

 Bay. They got the trepang by diving, in from three to eight fathoms 

 water; and where it is abundant, a man will bring up eight or ten at a time. 

 The animal is split down one side, boiled, and pressed with a weight of 

 stones ; then stretched open with slips of bamboo, dried in the sun, and 

 afterwards in smoke, when it is fit to be put away in bags, but requires 

 frequent exposure to the sun. A thousand trepangs make upicol., of about 

 125 Dutch pounds ; and one hundred picols is a cargo for a prow." 



Order 5. Sipunculidea. These are sometimes included in the order 

 Holothuridea, with which they agree in the tentacles, the intestinal canal, and 

 circulatory system, although they want the tubular feet. Sipunculus (pi. 74, 

 Hg. 7, and pi. 77, Jigs. 27, 28). According to Quatrefages the anatomy of 

 Echiurus indicates an afiinity both to the chffitopodous annelida and to 

 Holothuria, giving it characteristics of distinct types. Some authors, as 

 Blainville and Gervais, place these animals among the Annelida. 



Class IIel^siintiies. 



The classification of the various forms of worms has been attended with 

 difficulties, some of which still remain, notwithstanding the efforts of 

 distinguished naturalists to ascertain their characteristics. The worms, 

 whose body is composed of a series of rings, as in the leech and earth-worm, 

 and whose nervous system is composed of a line of ganglia, united by a 

 double nervous cord, as in insects, form with these the division Articulata, 

 of which they constitute the class Annelida. 



After excluding the Annelida from the class of worms, there still remain 

 many forms, both aquatic, and living in the interior of other animals, to 

 which the term Ilelminthes is restricted. Here the annulate structure has 

 disappeared, and the median nervous system has been separated into two 

 distinct branches, usually arising from a large ganglion anteriorly, or two 

 ganglia united by a transverse branch. From the characteristics which 

 these animals afford, it is difficult to decide whether they belong to the 

 radiate or articulate division of the animal scale, or, as is probable, form an 

 246 



