198 UNSEGMENTED “WORMS.” 
GENERAL ACCOUNT OF NEMERTEA 
In appearance most Nemertines are ribbon- or thread-like, and the 
cross-section is generally a flattened cylinder. They show a greater 
diversity of size than any other ‘‘ worms,”—from a Lz7eus, 12 or more 
feet in length (25 metres has been recorded for an extended Lzvevs 
Zongisstmus), to the pelagic Pelagonemertes, which is under an inch. 
The, colours are often bright, and tend to resemble those of the sur- 
roundings. The ectoderm is covered with numerous short cilia, and 
FIG. 104.—Transverse section of the Nemertean Drepanophorus latus.. 
—After Birger. 
@.x., Dorsal or proboscis nerve; P.s., proboscis sheath; P.c., proboscis 
cavity; P.s’., sac of proboscis cavity; d.v.2., dorso-ventral muscles ; 
c.m., circular muscles ; Z.7., longitudinal muscles ; Z.7., lateral nerve 
with branches; P., parenchyma; g., gut; Zv.., lateral blood vessel, 
beside which lies an excretory vessel ; #.4., excretory pore; d.v’., dorsal 
blood vessel; ZZ. epidermis. 
many of its cells are also glandular, secreting the mucus, which often: 
forms a tube around the animal, or is exuded in movement. Beneath 
the epidermis there is a parenchyma, consisting in part of connective- 
tissue, and often in part gelatinous. The body is remarkably con- 
tractile, and in some cases the spasms result in breakage. The muscles. 
are circular and longitudinal, and often also diagonal. The fibres are 
striped. In the adult there is no distinct coelom, the space between: 
the gut and the body wall being filled up with gelatinous connective 
tissue. In the larvae, however, a body cavity may be seen, either as an. 
archiccele, z.e. the persistent segmentation cavity (Zzweus obscurus), on 
