BALANOGLOSSUS. 435 
Dotichoglossus, Piychodera, Schizocardium, and Glandiceps. 
They are very widely, though locally, distributed, and most 
occur in the littoral area. 
DESCRIPTION OF BALANOGLOSSUS 
Form and habitat.—The species which form this genus 
are worm-like marine animals, burrowing in sand and mud 
in almost all seas. They vary in length from about 1 in. to 
over 6 in., and are brightly coloured and have a peculiar 
odour, like that of iodoform. ‘The sexes are distinct, and 
are marked externally 
by slight differences in 
colour. The body con- 
sists of a prominent 
turgid and muscular 
“proboscis,” a firm 
“collar,” a region with 
gill-slits, and, finally, a 
long, soft, slightly coiled 
portion. 
Skin and muscles.— 
The epidermis is ciliated, 
and exudes abundant %= 
mucus from unicellular Fic. 234.—Male of Balanoglossus (Do- 
glands. With theaddi- “choglossus) kowalevskit.—After Bate- 
tion of grains of sand, S ; 
the mucus sometimes Nos. t"Gperculum behind the collar; then the 
forms a tube round the _ region with gill-slits; zs., testes ; a., anus. 
body. Some species are 
phosphorescent. The muscular system is best developed 
about the proboscis and collar, which are used in leisurely 
locomotion through the soft sand. There are external 
circular and internal radial and longitudinal muscles. The 
fibres are unstriped. There is great regenerative capacity. 
Nervous system.—The dorsal nerve-cord is most de- 
veloped in the collar, but is continued along the whole 
length. It arises as a longitudinal groove of ectoderm and 
often remains tubular, like a typical spinal cord. The 
dorsal nerve-cord is connected by a band round the collar 
with a ventral nerve. There is also a nervous plexus 
Mo., Mouth; o/., 
