6 K. MITSUKUEI : STUDIES ON 



tentacles in their contracted state, and in part to actual individual 

 variation. 



Ambulacral appendages minute, without end-plates, but their 

 shape is more like that of a bluntly ending pedicel than of 

 a conical papilla. The smaller ones among them are no larger 

 than 0.16 mm,, while the larger ones are as much as 1.5 — 2.0 

 mm. in length. They can, especially in the larger specimens, be 

 recognized only by the openings or canals seen to enter them 

 from inside. Ambulacral appendages are most numerous on each 

 side of the two lateral ambulacra, which run along the some- 

 what thickened edge between the dorsum and the ventrum. 

 They are especially numerous in the posterior parts or in those 

 parts which project on each side of the vertical pygal furrow, 

 where, when foreign particles have been cleared off, they 

 project, giving a villous appearance. The largest appendages are 

 along these two ambulacra. On the two dorsal and the median 

 ventral ambulacra, small appendages are found along the two 

 sides of each ambulacrum. These arc minute, sparse, and can be 

 seen only when the skin has been mounted as a whole and 

 examined under the microscope. 



Calcareous deposits, ordinarily none in the perisome. But in 

 one specimen that 1 subjected to a thorough examination, there 

 were two calcareous bodies, one on each side of the cloacal 

 opening. On the one side, the body is of a somewhat peculiar shape : 

 it is cup-shaped, the open part consisting of an open lattice- 

 work, while the basal part (turned toward the posterior end) is of a 

 closer latticework. The body on the other side is somewhat l^roken, 

 but when complete, it must liave been of the same shape. Also in 

 a second specimen, which I subjected to a thorough search, there 

 was on each side of the cloacal opening a calcareous body. 



