dolichoglossus (balanoglossus) 233 



ENTEROPNEUSTA 



DOLICHOGLOSSUS (BALANOGLOSSUS) KOWALEVSKII 



In the natural habitat, note the character of the bottom 

 where Dolichoglossus is found. Is the sand clean or is here 

 an admixture of organic material? Note the frail tube of 

 sand particles fastened together with mucus, and the numer- 

 ous "castings." The animal has a characteristic and un- 

 pleasant odor. 



Note the division of the body into three general regions: 

 (1) a yellowish-white conical proboscis; (2) the collar, which 

 is brilliant orange-red, especially in males, with a white ring 

 posteriorly; and (3) the trunk, which is mainly orange- 

 yellow, shading to a greenish-yellow in the transparent pos- 

 terior region, which is often broken off when the animal is 

 collected. 



The trunk may be divided into the following regions, 

 which overlap: (a) an anterior branchial region, bearing on 

 each side not far from the dorsal median line a row of trans- 

 verse gill slits; (b) a genital region, bearing on each side of 

 the body an irregular and broken fold or ridge containing the 

 reproductive organs, which are gray in the female and yellow 

 in the male; (c) a posterior abdominal region, of much 

 smaller diameter than the rest of the body. 



The mouth is situated on the ventral side at the base of 

 the proboscis, and is concealed by the free anterior edge of 

 the collar. The animal is unable to close its mouth, and in 

 burrowing a continuous stream of sand passes through the 

 alimentary canal, forming the "castings" which are abundant 

 in the natural habitat of the animal. What must be the na- 

 ture of its food? 



Burrowing is effected partly by muscular contractions of 

 the body wall, but mainly through the power of the proboscis 

 and collar to become turgid. In burrowing and feeding, of 

 what use to the animal is the collar? 



Note the characteristic coiling of the genital region in 

 this species. The anterior end, including the branchial re- 



