376 Messrs Forbes and Goodsir on the Natural History 



tube with aerated blood. The use of the large trunk which 

 comes off from the ventral vessel, is evidently to supply the 

 mouth, trunk, and anterior part of the digestive tube, with ar- 

 terial blood, when the animal has projected the anterior part of 

 the body, and when the constriction of the snout, and the pres- 

 sure of the sand in which it is boring, would prevent the free 

 circulation of the blood in the two vascular circles, at times 

 when the supply is absolutely necessary from increased mus- 

 cular action. 



The nervous system is very simple, being merely a ring 

 surrounding the anterior part of the pharynx when it becomes 

 continuous with the skin. From this ring a nervous cord 

 runs along the under side of the animal to the extremity of 

 the body, terminating abruptly by sending off a few branches. 

 Along its course the cord gives off numerous lateral twigs, 

 which are unsymmetrical, and continue free for a short dis- 

 tance from their origin, and then disappear in the muscular 

 parietes of the body. "When the animal is contracted, the 

 cord is arranged in close undulations, and exhibits no gangli- 

 onic enlargements. It consists of a moderately long sheath, in 

 which the nervous matter is contained in a very soft condition. 



The reproductive system consists of four sacs which open 

 on the ventral surface by minute orifices, two immediately 

 behind the genital hooks, the other two about an inch far- 

 ther back, and both pairs about one-third of an inch from the 

 median line. When the Echiurus is not in season, they are 

 about one inch and a half long, one-fourth of an inch in diameter, 

 highly transparent, so as to be almost invisible, and possessed 

 of the power of twisting in all directions. When the male is 

 in season, they become greatly enlarged, four inches long, 

 half an inch in diameter, with one or two contracted portions. 

 The contained fluid is milk-white, and rather consistent ; and 

 when examined under a high power, it is seen to swarm with 

 exceedingly active globular Spermatozoa, which exhibit rapid 

 whirling and dancing motions. The male organs, when in 

 this condition, are remarkably beautiful objects, being cover- 

 ed with large thread-like and transparent scarlet bloodvessels, 

 which are relieved by the dead cream- white of the organs them- 

 selves. We have not seen the female sacs fully distended ; 

 when moderately so, the eggs appear to be arranged as in the 



