EXPLANATION OF PLATE VIII. 



FIG. 



1-17. GRANTIA COMPRESSA, Bowerbank, a calcareous-spiculed sponge. i, Small 

 intraspjcular area, showing pavement or.tesselated arrangement of collared 

 monads;/,/, pore apertures, x 800 ; 2-8, various polymorphic forms assumed 

 by the collared monads, X 1600 ; 9-12, small isolated groups of collared 

 monads from the same sponge, exhibiting various conditions of metamor- 

 phosis, some of them with simply the collars withdrawn and flagella remaining 

 extended, others with both these organs retracted and the body sarcode pro- 

 duced in form of pseudopodia, and in consequence presenting an amoebiform 

 contour ; at 9, the monads' bodies filled with ingested carmine particles ; 1 3, 

 an isolated monad with collar and flagellum retained in combination with 

 a long, bifurcated, posteriorly produced pseudopodium ; 15 and 16, amoebi- 

 form phases of collared monads of the same sponge ; 17, a metamorphosed 

 collared monad, with radiating pseudopodia, presenting an Actinophrys-like 

 aspect. 



18-31. HALICHONDRIA PANICEA, Johnston, a siliceous-spiculed sponge. 18, Group of 

 collared monads attached to a slender acerate spicule, x 1000; 19-23, 

 groups of collared monads attached to spicula, and in most instances 

 partially immersed within a thin stratum of structureless cytoblastema, ex- 

 hibiting various phases of metamorphosis ; 24, a group of metamorphosed 

 collared monads presenting an amoeboid aspect ; 25, very young, simply 

 monoflagellate, collared monads attached to a spiculum, x 1000 ; 26-31, 

 isolated amoebiform phases of collared monads of the same species, those in 

 the last three instances having capitate pseudopodia, and presenting an 

 Acineta-like contour. 



32-40. ASCETTA PRIMORDIALIS, Hkl, a calcareous-spiculed sponge (after Haeckel). 

 32-38, Metamorphosed collared monads, x 700 ; 39 and 40, amoebiform 

 zooids or cytoblasts, from the cytoblastema, the example in the latter instance 

 possessing two nuclei or endoplasts, and representing either two recently 

 coalesced zooids, or one about to divide by fission, x 700. 



41. LEUCOSOLENIA CORIACEA, Bwbk. Portions of transparent cytoblastema sur- 



rounding a poral aperture, and containing amoebiform cytoblasts enclosing 

 ingested carmine particles, X 800. 



42. Portion of cytoblastema of HALICHONDRIA PANICEA, containing amcebiform 



cytoblasts in various stages of development, those of the smallest order 

 originating from sporular bodies, x 1500. 



43. APLYSILLA SULFUREA, F. E. Sclz. Associated cytoblasts, with attenuate and 

 interconnecting pseudopodia, x 400 (after F. E. Schulze). 



