NOTE ON A NEW DEEP-SEA ECIUUROID, PROTOBONELLIA MITSUKURII, 2ÓI 



Bonellian species. The main stem is very narrow; its proximal part how- 

 ever abruptly dilates into a thin-walled vesicle near the rectal junction. 

 This dilation does not seem to be an artefact; for the condition is the same 



both in the right and left glands. 

 Both the vesicular and the tubular 

 parts are provided with the funnels 

 as well. The main stem gives off a 

 certain number (12 — 15) of side- 

 branches, each of which bears 2-4 

 long stalked funnels. The latter be- 

 come gradually fewer towards the an- 

 terior end of the main stem. No 

 rectal gland is present. 



/ 'entrai hooks. — When examined 

 from inside of the integument, 

 the radices of the ventral hooks are 

 seen as two comparatively long rods, 

 the sheaths of which have a very 

 complex system of muscles (figs. 2 



Fig. 2.- Viscera insita, highly magnified.--; and 3, rm). The so-called radial 

 — anal glands: am — accessory ventral vessel o . 



"ring-vessel"; ^/-collateral intestine;^— dorsa muscles are exceedingly numerous, 



vessel ; ///—funnel of oviduct ; ht — heart ; niv — . . 



nemo-intestinal vessel; oi-oviduct ; rm- arising from the integument in seve- 

 radial muscles of the hooks; tm— ventral nerve- 

 cord ; vv— ventral vessel. ral apparently concentric rows and 



being inserted not only to the apex, but also to the whole length of the 



radix, (see fig. 3). Of these muscles, the innermost ones are arranged in 



one plane, thus giving to the whole group an appearance of a half cone. 



There is another peculiarity concerning the shape of the interbasal muscle 



(fig. 3, ini) of the ventral hooks. Contrary to all cases hitherto known, 



this muscle is not a slender thread extending between the apices of 



the hook-sheaths, but represents a very wide membraneous structure 



stretching between the whole length of the two sheaths. It was ascertained 



under a high power that the majority of the component fibres of this muscle 



run horizontally, the rest pursuing an oblique course. Owing to the fine- 



