THE HOLOTHURIOIDEA 



219 



.t ,br 



FIG. I. 



1. Holothuria forskali, D. Ch., opened along the right side of the median "dorsal" line; 

 the blood-vascular system is not represented ; 2. Left side view ; and 3. Anterior view. 



4. Calcareous ring of H. forskali; the anterior ends are turned inwards. 



5. Diagram of the water-vascular system of H. forskali. illustrating the Actinopod plan. 



6. Larva of a Holothurian. (After Balfour.) 7. Auricularia larva ; and 8. Barrel- 

 shaped larva of Synapta digitata. (Both after Semon ; cf. Chapter VIII., Figs. III. & XVII.) 



9. Portion of the intestine with the accompanying blood-vessels and rete mirabile of 

 Holothurio, tubulosa. (After Tiedemann.) 



10. Left side view of Ankyroderma affine, Dan. and Kor. ; and 



11. Spicules of the same. (After Danielssen and Koren.) 



a, anus ; an, anchor ; a.v, anti-mesenterial blood-vessel ; br, brim ; e.b, ciliated band ; c.c, 

 circular water-vascular canal ; d, rectal "cloaca" ; c.o, Cuvierian organs ; r.r, collateral blood- 

 vessel ; d.mes, dorsal mesentery ; g, gonad ; i, intestine ; i.p, interradial piece ; l.d.r, left dorsal 

 radius ; 1. v.r, left ventral radius ; l.r.t, left respiratory tree ; m, mouth ; md, madreporite ; m.r, 

 median ventral radius ; m.v, mesenterial blood-vessel ; ot, otocyst ; p, podium ; p.c, podial 

 canal ; pp, papilla ; p.v, Polian vesicle ; r.cc, radial canal ; rd, spatulaterod ; r.d.r, right dorsal 

 radius ; re, rete mirabile ; r.p, radial piece ; r.r.t, right respiratory tree ; r.v.r, right ventral 

 radius ; s.c, stone-canal ; sp, spicules ; t, tentacle ; t.a, tentacle ampulla ; t.c, tentacle canal ; 

 x, oesophagus. 



