SPONGIIDA. 
4 8 pong. 
peripheral part, and are formed as a cuticular excretion of certain 
specially-modified connective tissue-cells, or spongoblasts, 
Easpongia^ (9) p. 613, characterized; species enumerated, E. officinalis, 
Linn., 1. c. p. 611, includes also E. mollissima and E. adriatica, Schmidt, 
and probably Spongia agaricina, Esper ; distinguished from E. zimocea, 
the only other Mediterranean species of the genus (vide infra). Six 
varieties distinguished from the Mediterranean ; viz., i., var. mollissima, 
pi. XXXV. figs. 1 & 2, Schmidt, = the fine Levantine bath-sponge of com- 
merce ; ii., lamella, pi. xxxvii. fig. 1, perhaps = S. agaricina, Esper ; iii., 
adriatica, pi. xxxv. figs. 1-4, pi. xxxvi. fig. 3, pi. xxxvii. figs. 1 & 8, 
pi. xxxviii. ; iv., irregularis, pi. xxxv. fig. 6 ; v., exigua, pi. xxxiv. 
figs. 6-7, pi. xxxv. figs. 6-8, pi. xxxvi. figs. 3, 8-11, pi. xxxvii. figs. 9 & 10; 
vi., tuhulosa, pi. xxxiv. fig. 8, pi. xxxvi. figs. 2, 4, & 12. The last three 
varieties are perhaps included in E. nitens, Schm. ; they have an 
irregular form, and oscula irregularly distributed on the surface. The 
varieties range in colour from black to yellowish-grey ; the positions 
and diameters of the oscula vary. Water-canal system described, 
p. 623, The arrangement of ciliated chambers and their ducts agrees 
in the main with those of Aplysina. Histology, p, 625. Of the three 
distinct body layers, the outer cellular layer is generally discernible, 
but in som9 cases a superficial cuticle overlies it ; the counective- 
tissiie layer contains contractile fibre-cells. Ciliated chambers have the 
shape of half or three-quarters of a sphere. The ova are developed 
in groups of 10-30. Sexes distinct. Some star-shaped cells, with dis- 
tinct walls, are formed at one stage of the transformation of the meso- 
derm ; in older embryos, the wall becomes thinner, and then resembles 
the s^me cells in late stages of Spongelia larvse, with whose ova and 
segmentation-stages those of Euspongia agree entirely. Aplysilla, too, 
seems pot to differ essentially in its ciliated larvae from these genera. 
Euspongia equina, Schm., Spongia gossypina and mceandriniformis. 
Duch. & Mich., (9) p. 614, are all referred to Ilippospongia, g. u., Schulze. 
Hircinia, Nardo, (10) p. 1. H. typica, flavescens, hirsiita, hehes, Schm., 
p. 11,= JI. variabilis, Schm., p. 12, pis. i. & iii. fig. 1, pi. iv., as mere varie- 
ties, not constant in form, colour, or character of surface. The surface 
is covered with a fine network, formed by the radiation of about ten 
broad fibres, which give off secondary fibres, from the point of each super- 
ficial prominence, or cbnulus ; all the fibres contain foreign particles. 
The water-canal system agrees with that of Euspongia and Gacosp>ongia. 
A pavement epithelium covers, as usual, the outer surface and the interior 
of the water-canals. The connective-tissue layer shows little that is 
peculiar. A partially distinct ovarian capsule lined by pavement epithe- 
lium occurs, as in other horny Sponges. The primary skeleton-fibres 
sometimes break up into networks. The secondary fibres are sometimes 
free from foreign bodies. 
Filaments of Flircinice, (10) p. 32 ; their character not definitely deter- 
mined ; form and structure of different kinds described ; their chemical 
composition and position in the Sponge agree better with the theory of 
their foreign origin than with any other. 
Sarcotragus spinosulus, Schmidt, (10) p. 26, = Hircinia, and distin- 
