546 W. WOODLAND. 
the absence of acidity, generally vanishes within a month or 
so, leaving, at any rate in the case of sponge, Aleyonarian 
and Cucumarian spicules, a distinct “sheath” as its sole 
representative, with traces of contained calcareous matter. 
As I have above stated, the “mould” is probably as much 
the product of the contained sclerite as this is of the 
‘“sheath”’ or investing ccenocyte. 
Hérouard (4), like Chun, has provided a very interesting 
account of the development of Holothurian spicules, and more 
particularly those which concern us in the present paper, viz. 
the perforated-plate spicules of Cucumariide; also, like 
Chun, he gives no figures in confirmation of his statements 
and, to again draw a parallel, I am sorry to say that these 
latter are equally as questionable, if not more so. Hérouard, 
whose excellent work on Holothurians should guarantee the 
trustworthiness of his statements, fully developed a preliminary 
note of his “Sur la formation des corpuscules calcaires chez 
les Holothuries,” published in 1887, into an elaborate descrip- 
tion of the process in his ‘‘ Recherches sur les Holothuries des 
cétes de France,” published in 1890. This description is, in 
brief, as follows:—The spicule commences as ‘fun petit 
tétraédre de carbonate de chaux,” secreted in the interior of 
a cell resembling an amcebocyte. Apparently four of these 
cells associate, and “le calcaire se dépose le long des parois 
de contact de quatre de ces cellules accoleés lune a l’autre et 
donne une production en forme d’z [see my fig. 9]. C’est 1a 
le centre du developpment, la charpente en quelque sorte du 
corpuscule. Les choses n’en restent en général par 14; quatre 
autres cellules placées symétriquement dans les angles formés 
par la réunion des quatre premieres entrent en jeu; elles 
déposent & leur tour du calcaire sur leurs parois de contact avec 
les précédentes et on obtient ainsi un corpuscule de la forme 
représenteé fig. B ci-dessous [a diagrammatic equivalent of my 
fig.11f.; Hérouard does not supply even diagrams of the cells]. 
D’autres cellules occupant les angles formés par ce groupe 
de huit cellules, entrant en jeu 4 leur tour, il se formera par 
le méme processus de nouvelles branches, et nous aurons 
