WORMS. 



231 



The EcHiuEiD^, which were formerly classed with the Gephyreans, are now known 

 to be true annelids, but their, precise affinities are uncertain, so we will slip them in by 

 appendix. They are easily recognized by the 

 pair of hooted bristles on the ventral surface, 

 and by the two crowns of bristles which occur 

 around the caudal extremity of some forms. 

 The three principal genera are Echiuris, Thal- 

 assema and JBonellia. The last-mentioned is 

 very striking in appearance, as will be seen by 

 the figure of Bonellia viridis. Oskar Schmidt, 

 referring to his visit to the Dalmatian island 

 Sesina, writes : " I noticed about a foot under 

 water, beneath a large stone, an intensely green 

 worm-like moving creature; I quickly lifted 

 the stone, and my supposed worm revealed 

 itself as the two-pronged proboscis of Bonellia. 

 We kept it alive in a basin for a day, and never 

 tired of watching its movements." The body 

 is covered with little warts, and, like the pro- 

 boscis, is vivid green ; it is capable of manifold 

 contractions and constrictions, and theproboscis 

 is an even greater proteus, and may stretch out 

 in large specimens to half a yard in length. 



Myzostoma is another puzzle to zoologists, 

 but is best guessed to be a degenerated para- 

 sitic annelid. The genus includes a consider- 

 able number of species which are all external 

 parasites of the Comatulas ; they are small, 

 disc-shaped, have four pairs of lateral suckers 

 on the ventral surface, and a retractile papil- 

 lated proboscis, and there are five pairs of 

 cirrus-bearing false feet. fig. 228. —Bmieiua viridis. 



Sub-Class III. — Enteropneusti. 



There now remains only one aberrant type for us to consider, namely, the whale's 

 tongue. The singular and little known animals we have studied as isolated forms do 

 not fall, readily into any of the great classes, and this very fact of their standing so 

 much apart renders them so much the more interesting to the thoughtful naturalist. 

 Many of these species are rare, and it becomes therefore the more desirable to call 

 general attention to them, in order that they may be sought and found by those who 

 might otherwise let precious opportunities go by unutilized. Very few of them have 

 yet been recorded from America, but there cannot be much question that many of 

 them, together with others equally singular but yet unknown forms, will, in the future, 

 be discovered in our fauna. 



The whale's tongue, JBalanoglossus, so named from a fancied resemblance, is a 

 very interesting animal to the scientific zoologist. The adult worm was originally 

 discovered at Naples ; the free-swimming embryo was subsequently named Tornaria, 



