76 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
body. The hypodermal layer is composed of a single 
layer of cubical cells. Underneath the hypodermis the 
chromatophores are found. The rest of the body wall is 
made up of connective tissue, in which groups of large 
adipose tissue cells occur. These last cells also occur in 
large numbers on the walls of the alimentary canal, and 
dorsal to the heart. (PI. IL., fig. 16, ad. ézs.) 
The body cavity (6.c.) is a haemocoel, the alimentary 
canal and other organs being in contact with the blood. 
A horizontal septum (sep.) divides the body cavity into a 
small dorsal pericardial cavity enclosing the heart, and a 
large sinus enclosing the other organs. 
The muscular system, excluding the muscles of the 
wall of the gut, heart, &c., consists of three sets of muscles 
-1, those in connection with the gastric mill; 2, the 
muscles moving the segments of the body; 3, the muscles 
moving the appendages. 
The muscles are composed of striated muscle fibres. 
The muscles controlling the gastric mill occupy almost 
the whole of the cavity of the cephalon and are very 
conspicuous on opening this. They are attached to the 
dorsal side of the cephalon, and most of them are inserted 
into the large lateral cardiac teeth. ‘The muscles moving 
the segments of the body are also segmented, but the 
muscle segments alternate with the body segments. On 
each side of the dorsal line there is a series of longitudinal 
muscles (d.d.m.). The anterior end of each bundle 
of muscle fibres of this series is inserted immediately 
behind the anterior end of one segment, and the posterior 
end is mserted at the anterior border of the succeeding 
segment. In the lateral regions, where the cuticle dips 
into the body, a number of oblique muscle bands, which 
form a series of muscles on each side, have their posterior 
ends attached to the anterior wall of the cuticular 
