PLATE I. 



HOLOTHUROIDEA. 



Figure 1 . CUCUMARIA FRONDOSA (Gunn.), Forbes. Natural size. 



2. A young specimen of the same, natural size. 



3. CUCUMARIA CALCIGERA (Stimp.), Seleuka. Natural size. 



4. Sketch of the mouth-ring and adjacent parts of a young individual, magnified. 



5. Generative tubes at an early stage of growth, magnified. 



6. Spicules of the superficial layer in situ, magnified. 



7. Small spicule in profile, magnified. 



8. Disk at the extremity of the sucker-foot, magnified. 



9. PSOLUS FABRICII (D. & K.), Liitken. Dorsal aspect, natural size. 



10. The same specimen. Ventral aspect, natural size. 



11. A young specimen. Ventral aspect, natural size. 



12. One of the small cup-like spicules of the ventral integument, magnified. 



13. Spicules of the ventral integument, magnified. 



14. CHIRODOTA L.EVIS (Fabr.), Grube. Natural size. 



15. Generative tubes, magnified. 



16. Portion of the mouth-ring, magnified. 



17. The pyriform infundibular organs or " Wimpertrichter," magnified. 



18. One of the wheel-like spicules, magnified. 



19. One of the sacculi, to show the aggregation of the spicules, magnified. 



20. MYRIOTROCHUS RINKII, Steenstrup. Natural size. 



21. One of the spicules, magnified. 



22. Sketch of the internal organs, showing the relative proportions of the alimentary canal, 



the Polian vesicle, and the generative tubes. 



23. Portion of the mouth-ring, magnified. (In this drawing the upward prolongations ought 



to taper more rapidly, and the foramina ought to be further up from the base.) 



24. Underside of the mouth-ring, with parts attached, seen from below, showing the dila- 



tations of the oral water-vessel. 



