36 EMBKYOLOGICAL MO^'OUKAPHS. 



PLATE XII. 



Development of Echinoidea, continued. Figures from Alexander Agassiz and C. "Wtville 



Thomson. 



Young Stages of 



1-3. Goniocidaris canaliculata. 17-22. Echinarachnius parma. 



4. Dorocidaris jmpillala. 23, 24. Encope emarginata. 



5, 6. Astkenosoma hystrix. 26-29. Conolmnpas Sigsbei. 



7. Diadema sclosum. 30-35. Hemiaster cavernosas. 



^-12. Afellita scx/oris. 36,36'. Spntangus purpurcus. 



13-14. McHita tesludinata. 37-40. Brissopsis hjrifera. 

 15, 16. McIIila Ungifissa. 



1-3. Goniocidaris catialicalala. From Alexander .Agassiz, The Zoology of the Voyage of H. M. .S. Challenger, 

 Vol. III. Tart I.X. Reiiort on the Echinoidea, PI. 11., London and Ediub., 1S81. 



1. Young specimen, 2 mm. in diameter, seen from the abactinal side. 



2. The same as lig. 1, seen from the actinal side. 



3. Another young specimen, 3 mm. in diameter, belonging to the long spined type of the species. 



4. Dorocidaris papillata. From Alexander Agassiz, Eevision of the Echini, Part II., 1872, PI. II«. 111. Catal. 



Mus. Comp. Zool., No. VII. Part II., 1872, PI. 11°. 



4. Young specimen, seen from the abactinal side, parti j' denuded. 2.4 mm in diameter. 



5, 6. Astlvcnosoma hystrix. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PL 11°. 



Quoted above. 



5. Part of test of young specimen, measuring 3.1 mm. in diameter, seen from the abactinal side. 



6. Part of test of same, seen from the actinal side. 



7. Diadema sctosum. From Alexander Agassiz, Revision of the Ei.-hini, Part II., 1872, PI. IP. Quoted above. 



7. Young specimen, measuring 2.4 mm. in diameter, seen in profile, showing the anal tnbe projecting between 



the spines beyond the level of the abactinal surface. 



8-12. Mellila sexforis. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PL XI. Quoted above. 



8. Young specimen, 2.4 mm. in diameter, having a Laganum-Iike shape ; the posterior interambulacral lunule is 



not as yet to be seen from the abaidinal side. 



9. The same from the actinal side, deeply concave, showing the commencement of the posterior interambula- 



cral hinule. 



10. Young sjiecimen, 4 mm. in diameter, seen from the abactinal side ; first trace of the posterior limule on the 



abactinal side. 



11. Young specimen, measuring 10.1 mm. in diameter, from the ab.actinal side. The ambulacral lunules all pres- 



ent, in different stages of growth. 



12. Young specimen, raea.suring 12. 7 ram. in diameter, witli all the ambulacr.il lunules completely pierced 



through and well formed. 



13-16. Mellita testiidinnta and longifissa. in which the lateral Innnles are formed from notches in the edge of the 

 test. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PL -XL Quoted above. 



13, 14. MeVitn tesludinata. 



13. Posterior interambulaei-nm of lig. 14, showing the posterior interambnlacral lunule, which in this type is 



formed from the lower side, as in ^[. sr.rforis, and forces its way through the test to the abactinal surface. 



14. Young specimen ('{), seen from the abactinal side ; the edge of the test shows as yet no trace of the notches 



so well developed in fig. l.'i. 



