THE GEPHYREA OF JAPAN. 17 



and of a deep brown color. Behind the anal region, the papillae 

 become gradually smaller until in the middle region of the 

 body proper they acquire the form of an almost flat body, 

 measuring 0.02-0.03 mm. across at base (Fig. 48). Structurally 

 these flattened papillae agree with those of the anal region. 

 The skin-surface here also is covered with small chitinous 

 thickenings of various forms and sizes peculiar to this region 

 (see the above figure). At the posterior end of the body the 

 papillae are once again of a somewhat conspicuous size : here 

 they measure on an average 0.05 mm. in height and 0.10 mm. 

 in diameter. These, in both their external and internal struc- 

 ture, are quite similar to those found in the middle region of 

 the introvert. No hook or any spiny structure is present on 

 the introvert. 



The longitudinal musculature forms a continuous sheath. 

 Only a single and very slender retractor muscle {rm, Fig. 49) 

 springs with two short roots from the posterior end of the body. 

 The intestinal convolution consists of about 20 irregularly twist- 

 ed spirals and is not accompanied by a spindle-muscle. The 

 intestinal spirals are joined to the body-wall by means of four 

 fine fixing muscles {fm), two of which are attached to the begin- 

 ning and the two others near the posterior end of the convolu- 

 tion. The dorsal vessel is about 15 mm. long ; it is not provided 

 with contractile villi. The segmental organ {so) is situated im- 

 mediately behind the anus as a single elongate sac lying on the 

 right side of the nerve-cord ; it is unaccompanied by a mes- 

 entery. No eye-spot is found on the ganglion. The tentacles, 

 about 10 in number, are filamentous. 



PhasGolion rectus agrees with Phascolion mancei^s Sel. & 

 De Man, in wanting the '' Haftpapillen " and the hooks and 



