SPONQIIDA. 
8 Sjpong. 
the Sponge, the structure and thickness of its walls, form and position of 
the central cavity, the manner of growth in the polyzoic forms, and especi- 
ally the presence or absence and structure of the rooting apparatus, 
furnish most important classificatory characters. 
Bossella philij)pinensisy Gray, (6) p. 273. 
Labaria hemisphcerica, Gray, (6) p. 275. 
Semperella schultzii, Semper, (6) p. 276, pi. xxiv. & xxv. figs. 18 & 19- 
Development of its spined spicules traced. 
Sclerothamnus, (6) p. 273. Marshall, in a note, modifies his original 
description of its canal system ; it is allied to Periphragella. The Syuau- 
loid group of Hexactinellids must be abandoned. 
Dactylocalyx pumiceus, Stutchbury, J. R. Micr. Soc. ii. p. 123, pis. vii. 
& viii. figs. 1-3, 6 & 7. Redescribed by Sollas ; the dermis contains 
long fine acerate spicules, sometimes terminally clavate ; alterations in 
skeleton take place with age, e.g.^ the hollow nodes are filled up. A 
new variety, var. stutchhuryi^ Sollas, described, 1. c. p. 131, pis. v. vi. & viii. 
figs. 4 & 5. 
Myliusia^ (6) p. 268. More nearly related to CcdoptycMum than to any 
recent Sponge, though the siliceous material is more developed on the 
exterior in the latter than in the former, and it is monozoic, not polyzoic ; 
the divergence between the spicules of the two may be got over by Prof. 
Zittel’s admission of the probable foreign origin of many of those as- 
signed by him to Cfxloptychium. 
Aulodictyon [-wm], (6) p. 272, defined. 
Calcarea. 
Ascetta, (1) pp. 367 & 371, has no gastrula stage, the mesoderm and 
endoderm are formed from an internal parenchymatous mass ; it must be 
considered as distinct from A scandra on embry ological grounds ; the latter 
with Sycandra and Leucandra represent another type. 
Ascetta blanca, (7) p. 358, pis. xxii. figs. 9-14, xxiii. figs. 16-21, has an 
external pavemout-epithelium ; the mesoderm cells are pale, with a few 
fine granules. Observations on development : the mesoderm- and endo- 
derm- cells are derived from the ciliated ectoderm-cells ; the endoderm 
does not form a continuous lining to the canal system ; food particles 
enter mesoderm- as well as endoderm- cells. 
Ascetta primordialis, (7) pp. 358 & 373, pis. xxii. figs. 3-5, 7 & 8, xxiii. 
figs. 1-15, has external pavement epithelium. Observations on develop- 
ment : neither early nor late does any clear distinction between the 
mesoderm- and endoderm- cells appear. 
Leucosolenia botryoides. G. Vasseur, Arch. Z. oxpor. viii. p. 1, figs. 1 
& 2, treating of the asexual reproduction of this Spouge, shows that closed 
buds are produced on the parent, covered with long, projecting acerate 
spicules about six times as long as those of the parent ; they become de- 
tached, and adhere to A Igce by their closed ends. 
Ute capillosa, Schmidt, described by H. J. Carter, Phil. Tr. clxviii. 
p. 288, Kerguelen Island. 
Sycandra, (7) p. 367, pi. xxi. figs. 5, 6, & 9-16. Invagination observed 
in the embryo ; fusion of ectoderm-cells into syncytium is only apparent ; 
