EXPLANATION OF PLATE VIIL 



Fig. 



1-17. Grantia compressa, Bowerbank, vol. i. p. 167, a calcareous-spiculed sponge. — 

 I, Small intraspicular area, showing pavement or tesselated arrangement of 

 collared monads ; p, p, 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 

 metamorphosis, some of them with simply the collars withdrawn and flagella 

 remaining extended, others with both these organs retracted and the body 

 sarcode produced in form of pseudopodia, and in consequence presenting an 

 amoebiform contour ; at 9, the monads' bodies filled with ingested carmine 

 particles ; 13, an isolated monad with collar and flagellum retained in com- 

 bination with a long, bifurcated, posteriorly produced pseudopodium ; 1 5 and 

 16, amoebiform phases of collared monads of the same sponge ; 17, a meta- 

 morphosed collared monad, with radiating pseudopodia, presenting an 

 Actinophrys-like aspect. 



18-31, Halichondria panicea, Johnston, vol. i. p. 167, a siUceous-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., vol. i. p. 167, 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., vol. i> p. 171. — Portions of transparent cyto- 



blastema surrounding a poral aperture, and containing amoebiform cytoblasts 

 enclosing ingested carmine particles, x 800. 



42. Portion of cytoblastema of Halichondria panicea, vol. i. p. 171, containing 



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

 order originating from sporular bodies, x 1500. 



43. Aplysilla sulfurea, F. E. Sclz., vol. i. p. 171.— Associated cytoblasts, with 



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



