THE ANATOMY OF SCALIBREGMA INFLATUM. 253 



the elevations become less marked, and in the posterior half 

 of the animal the skin is subdivided only by the circular 

 grooves which separate the annuli. 



Around the bases of the notopodia and neuropodia of the 

 segments immediately behind the branchial region there ni-e 

 sometimes epidermal elevations of considerable size. These 

 are best developed in old specimens (see figs. 1, 5). 



Sections of old specimeiis show that the yellow-brown 

 colour of the skiu is due to the presence of numerous insoluble 

 yellow granules in the epidermal cells. These granules are 

 light yellow when viewed singly, but appear brown in the 

 aggregate. 



There is only a small amount of connective tissue between 

 the epidermis and the underlying musculature. 



8. Musculature. 



Immediately beneath the epidermis there is a layer of cir- 

 cular muscles, beneath which are the longitudinal muscle 

 bands which project into the coelora (fig. IG). The circular 

 muscles in old specimens usually form a continuous sheet 

 beneath the epidermis, but in younger ones are sometimes 

 subdivided into hollow hoops, of which there are two (oc- 

 casionally only one) in each aunulus (fig. 12). 



The longitudinal muscles are interrupted along three lines, 

 viz. on each side at tlie level of the insertions of the oblique 

 muscles, and mid-ventrally by the nerve-cord (fig. 16). They 

 are thus divisible into three groups, of which the two ventral 

 lie between the nerve-cord and the insertions of the oblique 

 muscles, the other formiug an uninterrupted series extending 

 over the dorsal and lateral regions of the body-wall. The 

 ventral bands are rather more strongly developed, especially 

 in young specimens. The longitudinal muscles are covered by 

 a very thin coelomic epithelium. 



The oblique muscles are present throughout the cheeti- 

 gerous segments of the body. They are short, thin, narrow 

 bands arising at the sides of the nerve-cord and inserted into 



