BALANOGLOSSUS 157 
‘dives under stones at or below low-water mark on the coast 
of New England southwards to South Carolina. 
Order 2. Enopla.—In the members of this group the 
‘proboscis is furnished with a style. Representatives of the 
order are the species of Tetrastemma (T. serpentinum 
Girard, Fig. 107) and of Nemertes. ‘The former is a little 
yellowish worm, common under stones on the coast of New 
England between high and low-water mark ; it has a slightly 
marked head with four dark eye-specks. 
Cuass VI.—NEMERTINA. 
Body ribbon-like or cylindrical, soft, extensible, ciliated externally, with 
a proboscis in a sheath opening by a pore situated above the mouth. Cir- 
culatory system approaching that of the Annulata. Sexual organs, duct- 
less sacs ; either with or without a metamorphosis. 
Order 1. Anopla.—Proboscis without a style. (Lineus, Meckelia.) 
Order 2. Enopla.—Proboscis with a style. (Nemertes, Malacobdella.) 
Crass VII.—ENTEROPNEUSTA (Acorn-tongue worms). 
General Characters of the Enteropneusta.—The re- 
markable worm, Balanoglossus (Fig. 108), the type of this 
class, combines characters peculiar to itself, with features 
reminding us of the Nemerteans, Annelids, Tunicata, and 
even the vertebrate Amphioxus, while its free-swimming 
larva was originally supposed to be a young KHchinoderm. 
From the fact that the central nervous system lies above a 
notocord, Bateson places it next to the Vertebrates. 
Balanoglossus aurantiacus (Girard, Fig. 108) is a long, 
cylindrical, soft, fleshy worm, footless, without bristles, but 
with a large, soft, whitish tongue-shaped proboscis in front, 
arising dorsally within the edge of the collar surrounding 
the mouth. At the beginning of the digestive canal is a 
series of sac-like folds, of which the upper or dorsal portion 
is respiratory, and separated by a constriction from the lower, 
