162 ZOOLOGY 
ever, are enlarged wedge-shaped cells which almost fill up 
the cavity of the cup. They form a secretion which passes 
out through the narrow opening. The mouth of this is 
protected by special horny plates, modifications of the 
cuticle. The papillae are scattered all over the body, and 
as they stand out from the surface, they give the animal a 
rough appearance. 
Within the ectoderm is a layer of circularly-arranged 
muscle fibres broken up into circular bands in the introvert, 
Fia.104.—The body of Phymosoma 
varians laid open by an incision 
a little to the left of the median 
dorsal line, so as to show the 
internal organs. The introvert 
is retracted, 
et 
Opening of introvert. 
Position of brain, the two eye- 
spots are shown. This marks 
the level of the head. 
Dorsal vessel. 
iS) 
Left dorsal retractor muscle. 
Left ventral retractor muscle. 
Generative ridge. 
Ventral nerve cord. 
Nephridia. 
Coiled intestine. 
Rectum. 
Spindle muscle. 
NS SUR go 
se So 
— 
C=) 
and forming a continuous sheath in the trunk; internal to 
this are the longitudinal muscles, continuous in the introvert, 
but arranged in about twenty anastomosing bundles in the 
trunk. Within this layer, the coelom is lined by flat epithelial 
