THE VICTORIAN NATURALIST. 



August, 1900. 



DEVELOPMENT of a CALCAREOUS SPONGE. 



TRIU/^PH Engraving 60. 



PLATE I. 



A. — Colony of Sycon raphanus showing two adult individuals and two small 

 ones in the olynthus stage. 



B. — Portion of a section of the Sponge, Grantia labyrinthica, showing an 

 embryo breaking loose from the embryo-containing cavity into a 

 flagellate chamber. 



A. I, 2, 3, 4.- Ovum in various stages of segmentation ; A. 5, blastosphere ; 



A. 6, 7, pseudo-gastrula ; B. and B. I, blastosphere (late stage); 



B. 2, amphiblastula ; B. 3, gastrula ; B. 4, three-layered embryo ; 

 B. 5, olynthus (section) ; B. 6, olynthus (external appearance). 



