168 K. MITSUKUEI : STUDIES ON 



Its course is much convoluted. The madreporic body is pear- 

 shaped, situated opposite the opening in the mesentery facing the 

 middorsal interradius. PoKan vesicle one, large, on the median 

 ventral ambulacrum. In one specimen, there was a second small 

 one on the left ventral interambulacrum. Calcareous ring, as in 

 many other Sticliopus-siiecies, has the dorsal part pushed further 

 forward than the ventral part. Hence, all the pieces except the two on 

 the ventral and dorsal median lines are obliquely disposed. Selenka's 

 statements that the interradialia are broader than the radiaha has 

 been thought by v. Maeenzellee to be incorrect, which opinion I 

 must share. Color varies greatly. I have seen two specimens (No. 

 1409) which are entirely white and must be considered as "albinos." 

 Again there are specimens which are of a deep, dark color ap- 

 proaching black without a single lighter spot. The most usual 

 colorations are as follows : Those that live among rocks along a 

 rocky beach have the dorsal surface of a variegated, mottled ap- 

 pearance with darker and lighter patches produced by the inter- 

 minolincr of brown and maroon. The animal looks like rocks 

 overgrown or encrusted at spots with small algae and other marine 

 organisms, the coloration without doubt serving as a protection. 

 Individuals of this coloration seem moreover to have a larger 

 number of tall papilloo. The ventral surface is of a red color 

 with the tips of the tube -feet white. Those that live on sandy 

 or muddy ground, probably among sea-weeds, have generally a 

 uniform dark-green color, so much so that they are known in 

 common Japanese as " Ao-namako " (green holothurian). These 

 seem to have fewer and shorter papillae. 



The specimens from Hokkaido and the northernmost part of 

 Honshu have taller and more numerous papillae, which are most 

 conspicuous in dried specimens. In those specimens, the papillae 



