242 PROFESSOE F. M. BALFOUR. 



The layer which I have spoken of as formed of circulai 

 fibres is formed of two strata of fibres which girth the body 

 somewhat obliquely (PL XVIII, fig. 25). In the outer stra- 

 tum the rings are arranged so that their ventral parts are 

 behind, while the ventral parts of the rings of the inner stratum 

 are most forward. Both in the median dorsal and ventral lines 

 the layer of circular fibres become somewhat thinner, and 

 where the legs" are attached the regularity of both strata is 

 somewhat interfered with, and they become continuous with a 

 set of fibres inserted in the wall of the foot. 



The longitudinal muscles are arranged as five bands (vide 

 fig. 16), viz. two dorsal, two lateral, and three ventral. The 

 three ventral may be spoken of as the latero-ventral and 

 medio-ventral bands. 



The transverse fibres consist of (1) a continuous sheet on 

 each side inserted dorsally in the cutis, along a line opposite 

 the space between the dorsal bands of longitudinal fibres, and 

 ventrally between the ventro-median and ventro-lateral bands. 

 Each sheet at its insertion slightly breaks up into separate 

 bands. They divide the body cavity into three regions — a 

 median, containing the alimentary tract, slime glands, &c., 

 and two lateral, which are less well developed, and contain the 

 nervous system, salivary glands, segmental organs, Ike. 



(2) Inserted a little dorsal to the transverse band just de- 

 scribed is a second band which immediately crosses the first, 

 and then passes on the outer side of the nervous cord and 

 salivary gland, where such is present, and is inserted ventrally 

 in the space between the ventro-lateral and lateral longitudinal 

 band. 



Where the feet are given off the second transverse band 

 becomes continuous with the main retractor muscular fibres in 

 the foot, which are inserted both on to the dorsal side and 

 ventral side. 



Muscular system of the feet. — This consists of the 

 retractors of the feet connected with the outer transverse 

 muscle and the circular layer of muscles. In addition to these 

 muscles there are intrinsic transverse muscles which cross the 



