THE WORMS 71 



within sandy beaches in tubular burrows lined with mucous, and 

 the situation of the burrow is always marked by a heap of coiled 

 string-like masses of sand cast out at its mouth. The creature is 

 about five inches long and so delicate that its own weight is suffi- 

 cient to break it into pieces, so that it must be dug and washed out 

 of the sand with great care. The front end of the body is, how- 

 ever, quite tough and muscular, and is elongate and acorn-like in 

 shape; although it is often expanded and contracted in life. Back 

 of this acorn there is a thickened, collar-like region, and then comes 

 the long, tapering, worm-shaped body. The acorn is usually yeliow 

 or (lull (U-ange, the collar darker orange, and the body greenish- 

 brown or brownish-purple, often mottled Avitli dull white spots. 

 The mouth is at the lower front edge of the collar, and the creature 

 f>'eds upon the minute organisms contained in the large quantities 

 of sand which it swallows. The intestine extends straight through 

 the body. The sides of the intestine in the forward part of the 

 body are pierced, however, Ijy numerous gill clefts which open to 

 the outside in a series of pores along both sides of the middle of the 

 back. Now, gill slits are peculiar to the vertebrates, being found 

 either in embryonic or adult life in every known vertebrate from 

 the lowest fishes up to man. Indeed, many naturalists have sup- 

 posed that Balanoglossiis might be a survivor of the ancient race 

 which long ago gave rise to the vertebrates. On the other hand the 

 larva of Balanoglos>iii.^ is free-swimming, and bears such a remarkable 

 resemblance to that of a starfish, or Echinoderni, that no one sus- 

 pected it to be anything else until it was reared and observed to 

 change into a Balanoglossiis. It is possible, therefore, that Balano- 

 glossiis is descended remotely from ancient forms which gave rise 

 to both the annelid worms and the Echinoderms. The discussion 

 of this interesting subject would, however, take us too far afield, 

 and the reader is referred to the table of references for further 

 accounts of this species. 



