THE C4EPHYREA OF JAl'AX. 21 



border. On the iiitrovert-bnsis and the posterior end of body, 

 the papilke are conspicuously large and elevated. Hooks about 

 0.07 mm. high, provided with two sharp teeth at the apex and 

 with warts (*' Runzeln ") at the base ; hook-rows about 15-17 in 

 number, between them small hook-papillœ (" Hakenpapillen "). 

 Eye-spots distinct. Tentacles, about 12, arranged in a semicircle 

 above the mouth. 



Longitudinal muscles 20-21, rarely anastomosing. Four 

 retractor muscles arising from the middle of the body-proper : 

 the dorsal pair from the lst-2nd and the ventral from the 5th- 

 6th longitudinal muscles. The intestinal convolution consists of 

 12-14 spirals, and has a fine spindle-muscle fixed at both ends. 

 The one fixing muscle present is bifurcated towards the intestinal 

 attachment. The segmental organs are half as long as the body 

 proper ; the anterior third or fourth of their total length is 

 fixed by a mesentery to the body-wall. 



In Japan this species has been collected from the Hokkaido 

 in the north to the Hiukiu Islands in the south. As in many 

 other cosmopolitan forms, the species shows remarkable variations, 

 especially in color, according to difterent surrounding conditions. 

 Specimens from the Riukiu (Loo-choo) Islands and the Ogasawara 

 Islands exhibit all the essential characters described by Selenka 

 (28) and other authors, — as, for instance, the black crescent-shaped 

 markings on the introvert, papillae and hooks of the same form 

 and size, &c. Those from the main island of Japan are in several 

 respects slightly different from the above mentioned form. Thus, 

 the individuals living among Ascidian colonies or eroded tufaceous 

 sandstone, show an extremely wide range of variation with regard 

 to the o-eneral color of the bodv and the size and color of tlie 



