PLATE X. 



EXPLANATION. 

 Fig. 



1-9. Leucosolenia CORIACEA, Bwbk., vol. i. p. 174. — I, Group of collared monads or 

 spongozoa, certain of them at a a having withdrawn their collars and flagella 

 and assumed a quiescent state, and others zX b b become divided by 

 segmentation into innumerable sporular elements, x 800 ; 2, small area of 

 the same sponge magnified 2500 diameters, as viewed by the author with a 

 ■j\,-inch objective; a, ordinary collared monads; b, one such monad with 

 collar and flagellum withdrawn, having entered upon a quiescent or encysted 

 state ; c, spore-spheres, produced by the segmentation of the metamorphosed 

 collared monads; d d, spores derived from the disintegration of the spore- 

 spheres, and scattered irregularly through the common mucilaginous cyto- 

 blastema, cyt ; sp, triradiate spicule; 3-7, spores in aggregate and isolated 

 conditions liberated from the investing cytoblastema, and in most instances 

 possessing single terminal flagella, x 2500; 8 and 9, spore-masses figured as 

 entoderm cells by Metschnikoff, x 400. 



10. ASCORTIS FRAGILIS, Hkl., showing 3.1 a a collared monads, and at (5 a group of 



sporular elements with flagellate appendages (figured by Haeckel as sperma- 

 tozoa), X 400. 



1 1. ASCETTA PRIMORDIALIS, Hkl. — A portion of the inner or lining wall ; a a, pore- 



apertures circumscribed by flagelliferous monads ; b b, spore-groups derived 

 by metamorphosis from the ordinary collared monads, interpreted by 

 Haeckel as sperm-cells ; c c, large amoeboid bodies derived from the meta- 

 morphosis and coalescence of similar collared cells, which develop later into 

 the characteristic ciliated swarm-gemmules, x 350 (Haeckel). 



12. Vol. i. p. 173. Spore-like bodies, found by the author associated with a species of 



Halichondria, x 600. 



13. Vol. i. p. 173. Spore-like mass from the interstitial substance of a species of 



Hymcniacidon, x 500. 



14, 15. Leucosolenia botryoides, Bwbk., vol. i. p. 173. — 14, An intraspicular area, con- 

 sisting of a film-hke expansion of transparent and structureless cytoblastema 

 in which are immersed collared monads in an encysted state, those tA a a 

 having become divided by segmentation into sporular elements ; at ^^, 

 similar spore-masses disintegrated and dispersed within the substance of the 

 cytoblastema ; f, a minute triradiate spiculum, developed within the cyto- 

 blastema, X 600 ; 15, an isolated sporocyst with contained spores from the 

 same sponge, x 1 200. 



