20(1 



K. MITSUKURI : STUDIES ON 



cxtunded. MDrouvcr, wlicii we look at them from inside, the 

 vesicles which arc {u-esent on the inside, corresponding to each of 

 the dorsal papilla?, are arranged in two rows, one on each side of 

 the ambnlacrum. The length of the papillaj is, in preserved 

 specimens, 0.7 — 1 cm. The lacunae in the ventral pcrisome, cor- 

 responding severally to each lateral pedicel and its three divisions, 

 are similar to the structures described in Lcdmogonc vlolacea. 



In the dorsal pcrisome, there are present large wheels, with 

 small wheels only in very small proportion, if present at all ; 

 some of the former arcs the largest in the whole body. They 

 have mostly nine s}X)kes (rarely eight, ten, eleven or twelve, 

 sometimes even sixteen) and six central holes (very rarely fom-, 

 seven or eight) ; the diameter measures 0,00 — 0.255 mm., 1)ut 

 commonly 0.10 — 0.18 mm. In dorsal papilla?, the basal part has 



large and small wheels. 



H^L/W^M I' 



Textfig. 37. 



llyodannon ijhimi : a — Calcareous 

 ring ; b — Largo wheel of dorsum ; 

 c — Small wheel ; d — Supporting 

 rod. (h—dx2m). I-lDterradialia; 

 R — Radialia. 



but toward the up^XT part 

 only small ones are pre- 

 sent. The small wheels 

 have the margin cre- 

 nate ; spokes eleven or 

 twelve, central holes four, 

 diameter 0.030 — 0.048 

 mm. 



While we may find 

 large " large wheels " in 

 small individuals and 

 small " large wheels " in 

 large individuals, there is 

 in many cases a striking 

 contrast in appearance be- 



