STUDIES IN SPICULE FORMATION. 231 
Studies in Spicule Formation. 
I.—The Development and Structure of the Spicules in Sycons: 
with Remarks on the Conformation, Modes of Disposition 
and Evolution of Spicules in Calcareous Sponges gener- 
ally. 
By 
W. Woodland, 
University College, London. 
With Plates 13—15. 
ContTENTSs. 
PAGE 
Part I.—Derscription or Spicute Formation 1n Sycons. 
Introductory : - 232 
The Spicules in Stoon pananata and 8. itiata ; . 934 
The Monaxon Spicule . : : ; . 240 
The Triradiate Spicule . : ‘ 5 . 243 
The Quadriradiate Spicule ‘ ; . 247 
The Relation of the Scleroblast to the Bpicule : . 250 
Part Il.—Tue Spicutes or Catcargous SPONGES IN GENERAL. 
Theoretical considerations : 
Conditions and Features of Lime Secretion in Calcarea nok 
The Modes of Disposition of the Spicules in Calcarea . 260 
Secondary Forms and other Features of the Spicules in Calearea 270 
The Phylogenetic Evolution of the Spicules in Calcarea 5 ty 
APPENDIX A : : : : : eho 
APPENDIX B : : : : : . 280 
DESCRIPTION OF PLATES : : - : = 281i 
Ir being my immediate intention to systematically study 
the subject of spicule formation in various animal groups, I 
VOL. 49, PART 2.—NEW SERIES, 17 
