STUDIES IN SPICULE FORMATION. 139 
Studies in Spicule Formation. 
VIII.—Some Observations on the Scleroblastic Development of 
Hexactinellid and other Siliceous Sponge Spicules. 
By 
W. Woodland, 
The Zoological Laboratory, King’s College, London. 
With Plate 7. 
THE contents of the present paper, though brief, represent 
the results of a year’s careful inquiry into the manner in 
which the spicules of siliceous sponges are produced by the 
silicoblasts of the organism. This subject having already 
attracted so much .attention from spongologists, most of my 
results necessarily have been to a large extent merely con- 
firmatory of those obtained by previous workers, and these, 
of course, I shall mention as briefly as possible. A few of 
my results, on the other hand, are new, and in one or two 
instances corrective of former work. 
My material has consisted of typical examples of both 
siliceous groups of sponges—the Triaxonida (Hexactinellida) 
and Tetraxonida (Tetractinellida and Monactinellida). Some 
of my specimens have been prepared by the osmic acid and 
picro-carmine method, already described in previous Studies, 
and others (the majority) with borax-carmine. The former 
is the better method. The Monactinellida (viz. young portions 
or buds of Tethya lyncurium, Hymeniacidon san- 
guinea, Halichondria panicea, Hsperella lingua, 
Siphonochalina coriacea, Axinella polypoides, 
