CHAPTER V. 
The W oem-Like Protochoedates,— Class Enteropneusta. 
Baianogiossus. * HE last > ancl at tlie same time the lowest, group of the Proto- 
chordates is typically represented by the marine Baianogiossus. 
Living buried in the sand or mud of the seashore, these worm-like creatures exhale 
a peculiar odour resembling that of the 
chemical substance termed iodoform, and 
secrete a copious supply of slime, to which 
adhere particles of sand, thus forming 
a protective tube for their bodies. At the 
front extremity of the creature, writes 
Mr. Willey, “ there is a long and extremely 
sensitive proboscis, which is capable of 
great contraction and extension, and is in 
the living animal of a brilliant yellow 
or orange colour. Behind the proboscis 
follows a well-marked collar-region, con¬ 
sisting externally of a collar-like expansion 
of the integument, with free anterior and 
posterior margins overlapping the base 
of the proboscis in front and the anterior 
portion of the gill-slits behind. (The gill- 
slits are seen in our illustration below the 
collar.) In the ventral middle line, at the 
base of the proboscis, and concealed by the collar, is situated the mouth. 
Following behind the collar is the region of the trunk or body proper, which, 
in the adult of some species, reaches a relatively enormous length, even extending 
to 2 or 3 feet. The ectodermal covering of the body consists in general of ciliated 
cells, among which are scattered unicellular mucous glands; the cilia, however, 
appear to be more prominent on the proboscis than elsewhere. In the region 
of the trunk, which immediately follows upon the collar-region, there are a great 
number of paired openings on the dorsal side of the body placing the anterior 
portion of the digestive tract in communication with the outer world. These are 
the gill-slits, and they are arranged strictly in consecutive pairs to the number 
of upwards of fifty in the adult. In their structure, and more especially in the 
possession of tongue-bars, they bear a remarkable resemblance to the gill-slits of 
the lancelet. This is particularly striking in young individuals. As the adult 
form is approached in the development, the bulk of the gill-slits sinks below the 
a young balanoglossus (much enlarged). 
