146 



3. Note on the Development of a Holothurian Spicule. 



By K. Kishinouye, Zoologist to the Department of Agriculture and Commerce, 



Tokyo, Japan. 



eingeg. 11. März 1894. 



During the last summer I obtained a pinkish white Holothurian 

 by means of a long line for bottom fish from a depth of about 300 

 fathoms at the west side of Oshima (Vries Island) , a volcanic island 

 near the mouth of the Tokyo Bay. From the lack of the literature on 

 the subject I can not identify the species. 



As I examined its spicules I found two kinds of them. One 

 (fig. a) is small, flat, irregularly round in outline and scattered all over 



the body. The other 

 kind (figs. ò,c) is found 

 on the dorsal processes. 

 It is large, round, con- 

 vex above and wheel- 

 shaped. The nave of 

 the wheel is large, flat 



Fig. 1. 



0/ 



Fig. 2. 



and over its large cen- 



tral hole a ]( shaped 

 piece is attached, di- 

 viding the hole into 

 four smaller ones. The 

 spokes are short, cy- 

 lindrical, twelve in 

 number. To the outer 

 rim and on the con- 

 cave side of the wheel, 

 twelve scale- like pro- 

 cesses are attached, 

 alternating with the 

 twelve spokes and turned towards the centre. These weel-shaped spi- 

 cules were found in various stages of development. 



The [spicule which I found in the most rudimentary condition 

 was a small rod with two horns at both the ends (fig. d). The distal 

 end of each of these horns is next expanded into a small trapezoidal 

 sheet (fig. e) . The trapezoidal sheet is joined to the horn almost per- 

 pendicularly at the middle point of its broader side. The upper and 

 the slanting sides of the trapezoid are gently concave. These sheets 

 are laterally expanded on its broader side and joined together (fig./). 

 At the point where two trapezoidal sheets unite , a tooth is produced. 

 Thus a dodecagon with its sides a little curved inwards and with four 



