382 P. HEEBERT CARPENTER. 



described by Perrier,^ whose excellent account and figures of 

 them seem, for a wonder, to have escaped the notice of 

 Messrs. Vogt and Yung. He writes as follows : 



" Imniediatement au-dessous de la couclie epitheliale se trouve im tissu par- 

 ticulier forme d'elements qui semblent relier entre elles la membrane cellu- 

 laire qui forme le tegument externe et la membrane qui revet I'axe calcaire du 

 bras. Ces elements sent incolores, fusiformes, et les extremites du fuseau, 

 qui souvent se bifurqueut, donnent naissance a des prolongements qui, apres 

 s'etre plus on moins divises, vienneut s'attacher a I'une des deux membranes 

 qui relieut ces elements. Dans la partie renflee de ces sortes de cellules 

 etoilees on aperfoit toujours uu noyau tres-brillant." 



The identity of these "elements etoilees" with Goette's 

 contractile cells is evident from a comparison of the excellent 

 figures given by both authors, and Perrier states expressly that 

 he has not observed them perform amoeboid movements or 

 contractions of any kind. He regards them as '^ surtout des 

 elements du tissu conjonctif;" and he proceeds to compare 

 them with the yellow oil-cells of Wyville Thomson, " corpus- 

 cles jaune clair et tres-refringents . . . qui se retrouvent 

 en plus ou moins grande abondance dans toutes les parties du 

 corps de Fanimal." Finding what appear to be several inter- 

 mediate stages between the two structures, he was led to the 

 conclusion that '' les elements etoilees et les gros elements 

 jaunes sont morphologiquement de meme nature, que ces 

 derniers ne different des autres que parce que la matiere jaune 

 a envahi tout Finterieur de la cellule et distend ses parois." 

 Now, however, we are told by Vogt and Yung that these 

 yellow cells which Perrier found to be universally distributed 

 in all parts of the mature Ante don rosacea, are really the 

 amoeboid spores of symbiotic algae, and that the sacculi at the 

 sides of the ambulacra and elsewhere are groups of " veritables 

 zoospores" of the same algae. According to their theory these 

 zoospores are later developmental stages of the yellow cells, 

 Perrier's connective-tissue elements. 



The contents of the sacculi were described by . Professor 

 Perrier^ in the following terms: 



' Loc. cit., pp. 51 — 53, pi. iii, fig. i I. 

 ^ Loc. cit., p. 67 ; pi. ii, fig. 7. 



