LARVAL SKELETON OF SPATANGUS 491 
of the parallel rods is a branch given out vertically from an 
arm of the calcification centre. 
6. The larval skeleton of Spatangus purpureus is 
characterized chietly by (a) more or less considerable length 
of the unfenestrated proximal portions in the latticed rods, 
(b) fusion of the tips of the ventral horizontal rods forming 
a thickened joint, (c) overlapping of the body-rods near their 
posterior ends, and subsequent fusion of this part so as to 
form an oblique cross, (d) rather simple appearance of the 
postero-lateral rods, and (e) formation of a calcareous plate 
on each side of the stomach in the oldest stage. 
REFERENCES. 
1. Chadwick, H. C. (1914).—‘‘ Echinoderm Larvae of Port Erin”’, 
‘Proc. Trans. Biol. Soc. Liverpool’, vol. 28. 
2. Krohn, A. (1853).—‘‘Uber die Larve von Spatangus pur- 
pureus”’, Miiller’s ‘ Arch, Anat. Physiol.’, 1853. 
3. —— (1854).—‘* Beobachtungen iiber Echinodermenlarven ”’, Miiller’s 
‘Arch, Anat. Physiol.’, 1854. 
4, MacBride, E. W. (1914).—** The Development of Echinocardium 
cordatum. Part 1. The External Features of the Develop- 
ment’, ‘ Quart. Journ. Micro. Sci.’, vol. 59, Part IV. 
5. Mortensen, Th. (1898).—‘* Die Echinodermenlarven der Plankton- 
Expedition”, ‘ Ergebn. Pl.-Exped. Humboldt-Stift.’, Bd. I, J. 
6. —— (1913).—* On the Development of some British Echinoderms ”’, 
‘Plymouth Journ. Mar. Biol. Ass.’, vol. 10, no. 1. 
7. —— (1920).—‘*‘ Notes on the Development and the Larval Forms of 
some Scandinavian Echinoderms”, * Vid. Medd. nat. Foren, 
Kjgbenhavn ’, Bd. 71. 
8. Miiller, J. (1848).—-‘‘ Uber die Larven und die Metamorphose der 
Ophiuren und Seeigel”’, “Phys. Abhandl. k. Akad. Wiss. Berlin’, 
1846. 
9, —— (1855).—‘* Uber die Gattungen der Seeigellarven. VII. Abhandl. 
iiber die Metamorphose der Echinodermen ”’, ibid., 1854, 
10. Prouho, H. (1887).-—‘‘ Recherches sur le Dorocidaris papil- 
lata’, ‘ Arch. Zool. Expér. Génér.’, 2° sér. 5. 
11. Théel, H. (1892).—‘‘ On the Development of Echinocyamus 
pusillus (O. F. Miiller)”’, ‘Nova Acta Rg. Soc. Sci. Upsala’. 
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