THE GEPHYREA OF JAPAN. 11 



found OU the skin-surface of the body proper ; we have here to 

 do with tolerably large, elongated sacs with a thin, colorless and 

 transparent wall. Fig. 36 represents one of the structures greatly 

 magnified. The organ is hollow ; its cavity communicates with 

 the body-cavity by a small aperture which is situated just at the 

 basis of the organ and is perfectly round in contour (Fig. 37). 

 As Fig. 37 shows, the wall contains a number of longitudinal 

 muscle- fibers [mf) running parallel to one another. A closer 

 microscopical examination shows that most of these muscle-fibers 

 are proximally continuous with the circular muscles of the body- 

 wall. From the structure and the relation of the organs to the 

 body-cavity, it seems very probable that they serve as the respira- 

 tory apparatus. They are found here and there all over the 

 surface of the body proper, but are most numerous in the posterior 

 region. 



The longitudinal muscles are everywhere continuous. The 

 inner surface of the body- wall is of a shiny appearance. There 

 exist two pairs of the retractor muscles, which are fairly long 

 and very slender. The ventral pair [vm, Fig. 38) spring from 

 the posterior border of the anterior one-third of the body proper, 

 while the dorsal pair arise about 7 cjii. in front of that border. 

 The sexual organs (sx) are developed as two narrow wavy bands 

 attached to the base of the ventral retractor muscles (vm). The 

 intestinal convolution {ic) is long and conspicuous, consisting of 

 about 20 double spirals closely twisted around the spindle-muscle 

 {s)/i) which posteriorly is not fixed to the body-wall. Three fixing 

 muscles {fm) are present. One of them originates inside the base 

 of the left ventral muscle and ends at the posterior free part of 

 the oesophagus. The other two are rooted each on one side of 

 the nerve-cord and are attached to the beginning of the rectal 



