Ill 



PORIFEKA 



45 



branched cells reminding 'us of the mesenchyme cells of the larva 

 of Grantia. 



FIG. 22. Seven stages in the metamorphosis and fixation of the larva and growth 



of the young sponge of Plakina monolopha. (After Maas. ) 



A, larva in amphiblastula stage ; granular cells budding off cells into interior. B, larva about to 

 fix itself. C, larva just fixing itself, flagellated half flat. D, fixed larva, flagellated cells beginning to 

 invaginate. E, " Rhagon " stage. F, G, two stages in subdivision of Khagon cavity by downgrowth of 

 septa ; fl, flagellated cells ; gr, granular cells ; mes, " mesenchyme " ; s, septa dividing cavity of Rhagon. 



After fixation the flagellated cells collapse to form a solid mass, 

 which is speedily separated into smaller masses by ingrowths of the 



