Ill 



POEIFEEA 



45 



branched/cells reminding Tus of the mesenchyme cells of the larva 

 01 Gra7iha. 



%// ^ 





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



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



A, larva in araphiblastula 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. B, " Bhagon " stage. F, G, tvi^o stages in subdivision of Rhagon cavity by downgrovrth of 



septa ; Jl, flagellated cells ; gr, granular cells ; mes, " meseucliyme " ; 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 



