P LA TE X . 



EXPLANATION. 



FIG. 



1-9. LEUCOSOLENIA CORIACEA, Bwbk. 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 certain of them at a a having withdrawn their collars and flagella and assumed 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 at 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 -y^-inch objective ; 

 , 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 withdrawn, having entered upon a quiescent or encysted state; c, spore- 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 cytoblastema, 

 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 at a a collared monads, and at b 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 metamorphosis 

 and coalescence of similar collared cells, which develop later into the charac- 

 teristic ciliated swarm-gemmules, x 350 (Haeckel). 



1 2. Spore-like bodies, found by the author associated with a species of Halichondria, 



x 600. 



1 3. Spore-like mass from the interstitial substance of a species of Hymeniacidon, x 500. 



14, 15. LEUCOSOLENIA BOTRYOIDES, Bwbk. 14, An intraspicular area, consisting of a 

 film-like expansion of transparent and structureless cytoblastema in which are 

 immersed collared monads in an encysted state, those at a a having become 

 divided by segmentation into sporular elements ; at b b, similar spore-masses 

 disintegrated and dispersed within the substance of the cytoblastema ; c, a 

 minute triradiate spiculum, developed within the cytoblastema, x 600 ; 15, 

 an isolated sporocyst with contained spores from the same sponge, x 1200. 



16-18. Sporocysts of a species of Halichondria, that at Fig. 1 8 burst and discharging 

 minute granular spores, x 600. 



