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. II., fig. 16, ad. tis.) 



The body cavity (b.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.l.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 inserted 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 



