STRUCTURE AND FUNCTION OF THE SPHARIDIA. 39 
On the Structure and Function of the Spheridia 
of the Echinoidea. 
By 
Howard Ayers, 
Of Ann Arbor, Michigan, U.S. America. 
With Plate V. 
LITERATURE. 
1. Lovén, S.—“ Etudes sur les Hchindidées,” ‘ Konig]. Svenska Vetenskaps- 
Akademiens Handlingar,’ Bd. xi, No. 7, Stockholm, 1874. 
2. Macxintosu, H. W.—“ On the Acanthology of the Desmosticha,” ‘ Trans. 
Roy. Irish Acad.,’ vol. xxiv, 1878. 
3. Acassiz, A—“ Report on the Echinoidea in ‘Challenger’ Reports,” ‘ Zool.,’ 
iii, London, 1881. 
4. Koruiter, M. Renti.— Recherches sur Jes Echinides des Cotes de Pro- 
vence,” ‘Ann. du Mus. d’Hist. Nat. de Marseille Zool. I,’ lére Partie, 
Marseille, 1882-8. 
A part of the following observations were made some two 
years ago while studying under Professor W. Faxon at the 
Museum of Comparative Zoology, Cambridge, Mass. ; the other 
part, with a repetition of the former observations, were made 
while studying the fauna of the Mediterranean coast of France 
at the Laboratoire Arago of Banyuls-sur-Mer. 
For the opportunity of enjoying the unusual advantages for 
sea-side study offered by the Arago laboratory I am greatly in- 
debted to its founder and director, Professor H. de Lacaze- 
Duthiers ; and I gladly use this opportunity to publicly acknow- 
ledge the great obligation under which I am placed by the 
liberality with which the facilities of the station were placed 
at my disposal. 
