SPONGIDA. 
8 Spong. 
Cellular outer layer £[alisar<^a lobularis (16). 
Mesoderm tissue in Halisarca pesembles ifec^usa-disk tissue (16) ; con' 
tains the ova and spermatozoa. 
Fine oanals in IJaliaaixa lined with flat ciliated epithelium up to the 
ciliated chambers (16). 
Sex: Halisarca lobularis is dioecious (16). 
Spermatozoa developed in numbers, as fine knobbed thread-like bodies, 
in mother cells (16) in JBf. lobularis. 
“Collar cells” essentially the same m Halisarca as in Calci- 
sponges. 
“ Persons.” Hyatt supports Hackel as to the part which these, by mul- 
tiplication and lateral fusion, play in the formation of the large Ceratosa ; 
the “ cloacae ” of the young being represented by various oscular pas- 
sages (9). 
Ovum : — After segmentation and formation of “planula” embryo, in 
Ascetta (14), some cells at the hinder pole become granular and push their 
way into the cleavage cavity^ which closes ; these endoderm cells may be 
merely scattered over the cavity, or accumulate at the lower end. 
Ectoderm (14). The cells may have an outer transparent part in 
Ascetta, but this is no pyncytium, and is probably only represented in 
fidult by the syncytium, whore present. Schulze (16) holds the adult 
superficial layer to represent it. 
Germ-layers. Three probably, Schulze (16); this disputed by Keller (10). 
Gastrula. Keller (10) considers an invaginate gastrula to be formed, 
with fusion of ectoderm into syncytium. Schmidt (14) denies formation 
of gastrula ; the “ amphiblastula ” is reached by “ shortened develop- 
ment.” Hyatt (9) also denies it for the Silicea and Ceratosa. 
Embryonic development results in a sessile form in Ascetta (14), with 
pseudopodiated outer membrane. 
A stage in which one end is open occurs in some Ceratosa after the 
“ morula” stage (9). 
Spongia agrees in the main with Chalina and the Halichondriida (8) in 
development, but has no skeleton in early stages. It has a good basal 
collar and area. 
Fossil Sponges. 
23. SoLLAS, W. J. On Stauronema, a new genus of Fossil Hexactinellid 
Sponges, &c. Ann. N. H. (4) xix. p. l,pls. i.-v. 
24. . On Pharetrospongia strahani, Sollas, a Fossil Holorhaphidote 
Sponge, &c. J. Geol. Soc. xxxiii. p. 242, pi. xi. 
25. Young, J., & Young, J. On a Carboniferous HyaZonma and other 
Sponges. Ann. N. H. (4) xx. p. 425, pis. xiv. & xv. 
Carter also refers to Young’s Hyalonema in a preliminary note in 
Ann. N. H. (4) xx. p. 176. Zittel, in addition to his “ Studies on Fossil 
Sponges ” (22) reproduces part of these in JB. f. Mineral. 1877, p. 337, 
pis. ii.-v., giving at the same time some very good figures of the micro- 
scopic structure of more than twenty of the noticed species (e.g., Trerna- 
