NOTES ON ECHINODERM MORPHOLOGY. 379 



Notes on Echinoderm Morphology, No. X. On 

 the Supposed Presence of Symbiotic Algae in 

 Antedon rosacea. 



By 



P. Herbert Carpenter, ]>.Sc., F.R.S., F.I..S,, 

 Assistant Master at Eton College. 



With Plate XXX, fig. 3. 



The anatomical monograph on Antedon rosacea which 

 has been recently published by Messrs. Vogt and Yung,^ con- 

 tains the exposition of a new theory as to the nature of the 

 sacculi, those problematical structures which have hitherto so 

 completely puzzled all the various naturalists who have devoted 

 any attention to the Crinoidea. These vesicular bodies^ to 

 which the name sacculi was given by Dr. Carpenter/ were 

 regarded by him as possibly sense-organs, by Edward Forbes 

 as ovaries, by Wyville Thomson as calcareous glands, and as 

 possibly excretory organs by Perrier/ with whom Ludwig^ was 

 inclined to agree ; while Vogt and Yung describe them as sym- 

 biotic algse.^ 



Colourless, or nearly so during life, they become strongly 

 tinged after death by the red pigment set free from the peri- 

 some (antedonin?), and they then appear as the red spots 



1 'Traite d'Anatomie Comparee Pratique,' Livr. 7, 8, pp. 519 — 572, 



^ "On the Structure, Physiology, and Development of Antedon (Coma- 

 tula, Lamk.) rosaceus," 'Proc. Roy. Soc.,' 1S7G, vol. xxiv, p. 227. 



^ " Recherches sur 1' Anatomic et la Regeneration des Bras de la Coma - 

 tula rosacea," 'Arch, de Zool. exp. et gen.,' 1873, T. ii, p. 67. 



"* " Beilrage zur Anatomic der Crinoideen," ' Zeitschr. f. wiss. Zool.,' 1877, 

 Bd. xxviii, p. 305. 



5 Op. cit., p. 570. 



