144 SYCANDRA. 



afresh (fig, 67 B, en,~) and develop the peculiar collar characteris- 

 tic of the hypoblast cells of the Spongida (vide fig. 64, hy.}. 

 When this stage of development is reached we have a fully- 

 formed sponge of the type made known by Haeckel as 

 Olynthus. 



FIG. 67. THE YOUNG OF SYCANDRA RAPHANUS SHORTLY AFTER THE DEVELOP- 

 MENT OF THE SPICULA. (Copied from Schulze.) 



A. View from the side. 



B. View from the free extremity. 



os. osculum ; ec. epiblast ; en. hypoblast composed of ciliated cells. The terminal 

 osculum and lateral pores are represented as oval white spaces. 



When young examples of Sycandra come in contact shortly 

 after their attachment they appear to fuse together temporarily 

 or else permanently. In the latter case colonies are produced 

 by their fusion. 



Amongst other calcareous sponges the larva of Ascandra contorta 

 (Haeckel No. 126, Barrois No. 122) presents the typical amphiblastula stage, 

 and so probably does that of Ascandra Lieberkilhnii (Keller No. 128). In 

 Leucandra aspera (Keller No. 128, Metschnikoff No. 134) the larva passes 

 through an amphiblastula stage, but the characters of the cells of the two 

 halves of the larva do not differ to nearly the same extent as in Sycandra. 



Although the majority of calcareous sponges appear to agree in their 



