The Protochordata 463 



a mucous substance is secreted, holding togetner particles by 

 which are formed tubes of sand. The animal has a peculiar 

 odor like that of iodoform. At the front is a long muscular 

 proboscis, very sensitive, capable of great extension and con- 

 traction, largely used in burrowing in the ground, and of a 

 brilliant orange color in life. Behind this is a collar which 

 overlaps the small neck and conceals the small mouth at the 

 base of the proboscis. The gill-slits behind the collar are also 

 more or less concealed by it 



The body, which is worm-like, extends often to the length 

 of two or three feet. The gill-slits in the adult are arranged 

 in regular pairs, there being upwards of fifty in number much 

 like the gill-slits of the lancelet. As the animal grows older 

 the slits become less conspicuous, their openings being reduced 

 to small slit-like pores. 



In the interior of the proboscis is a rod-like structure which 

 arises as an outgrowth of the alimentary canal above the 

 mouth. In development and structure this rod so resembles 

 the notochord of the lancelet that it is regarded as a true 

 notochord, though found in the anterior region only. From 

 the presence of gill-slits and notochord and from the develop- 

 ment and structure of the central nervous system Balanoglossus 

 was recognized by William Bateson, who studied an American 

 species, Dolichoglossus kowalevskii, at Hamp- 

 ton Roads in Virginia in 1885, and at Beau- 

 fort in North Carolina, as a member of the 

 Chordate series. Unlike the Tunicates it 

 represents a primitively simple, not a degen- 

 erate, type. It seems to possess real affinities 

 with the worms, or possibly, as some havej 

 thought, with the sea-urchins. 



A peculiar little creature, known as Tor- 

 naria, was once considered to be the larva 

 of a starfish. It is minute and transparent, 

 floating on the surface of the sea. It has no 

 visible resemblance to the adult Balanoglossus, FIG. 275.^"' ' Tornaria ' 

 but it has been reared in aquaria and shown ^rvaof Glossobalanus 

 to pass into the latter or into the related 

 genus Glossobalanus. No such metamorphosis was found by 



