A CONTRIBUTION TO THE ANNELIDA. 59 
other means. Shortening and elongation of the organs may 
occur without the presence of circular fibres. 
The absence of specially developed branchie in Spinther is 
interesting, but the perivisceral fluid as well as the blood- 
vessels are in this form nearer the surface, and the great hypo- 
dermic membranous flaps on the dorsum may in some respects 
also subserve this function. The intimate connection of the 
lateral lamelle with the bristles may also prove of importance, 
since the muscles of the bristles must cause extension of the 
membranous lamelle. 
Dorsal Cirri.—Externally is the somewhat granular layer 
covering the cuticle, a condition probably due to the cilia, 
which Ehlers describes as being largely developed. A thick 
layer of hypoderm occurs beneath, with large cells here and 
there. Both layers are continuous with those on the body. 
The hypoderm at the extremity of the cirrus is finely granular 
and longitudinally streaked, and the cuticle of this region is 
very thin. Vertical fibres from the body pass upward into the 
base of the cirrus and thence to the tip of the organ. Only a 
few circular muscular fibres were observed at the base of the 
cirrus (under the hypoderm), the elasticity of the cuticle pro- 
bably sufficing to restore the shape of the organ on relaxation 
of the longitudinal fibres. These organs are not represented 
in § pinther. 
Alimentary Canal.—On viewing the alimentary canal 
from the dorsum in a spirit preparation of Euphrosyne 
foliosa (Pl. 7, fig. 2) the proboscidian region (Schlundkopf, 
Schmarda) has a somewhat ovoid outline, and is slightly 
narrower in front than behind. It is divisible into two regions, 
for anteriorly a glistening whitish layer (a) envelops like a 
sheath rather more than the anterior third, splitting in the 
middle line and curving outward on each side, so that its out- 
line resembles that of a bivalve shell. Inferiorly this sheath 
preserves an unbroken transverse border posteriorly. The 
enlarged posterior region is free beneath, but dorsally termi- 
nates in a canal (6) connecting it with the intestine at d. The 
outline given in Pl. 7 differs considerably from the organ in 
