PORT F ERA 



21 



ectoderm and entoderm. Lastly, there occurs at the apical 

 pole an evagination of the body- wall like a chimney-pot, at 



r^ iiJ J nA ^ ■ — 



Fig. 6. — Development of Osearella, diagrammatic (after Hbideh). A, swarming 

 blastnla larva ; B, attached gastrula-stage ; C, stage initiating the closure of the 

 gastrula mouth {Gm) and the folding of the entodermic sac ; D, young sponge ; Os, 

 osculum })o, inhalent pores ; Ee, ectoderm ; Ea, entoderm. 



