SPONGIIDA. 
12 Sjcong, 
specific character (20), as in the case of the skeleton spicules of the above 
varieties of Sjpongilla mentioned (I. c.). 
Form of spicule, as constant for one species, also thrown in doubt (20). 
Canal system of Calcarea (9) homologous with gastral cavities of Ccel- 
enterata. 
Projecting spicule-points used to detain food matter, (14) p. 8. 
Nourishment of parts of Sponges by absorption of matter dissolved in 
the water, (14) pp. 12, 26, probable in some cases. 
Starch detected in cells in seven species of Silicea (9), but in no Calci- 
sponge, Halisarca, or Gumminean. 
Sjpongilla (8), p. 196. The egg undergoes an equal, total segmenta- 
tion, producing a solid Morula, the ectoderm enclosing the endoderm 
by its rapidity of growth. A closed cavity formed within the darker 
endoderm cells converts it into a Planogastrula. The primitive endo- 
derm separates into endoderm and mesoderm. A body-cavity space is 
formed between the latter and the ectoderm. Ciliated chambers formed 
by evagination of endoderm after fixation of larva. Mouth opening made 
by the falling apart of the upper mesoderm and endoderm cells. 
The developmental stage in S. rajphanus (16), which follows that of the 
flattened form with narrow cavity and upper division of small cells 
and lower one and ring of large ones, shows an enlargement of the cavity 
at the expense of the cells. A partial invagination of the granular cells 
may occur. The ciliated cells are then pressed inwards, and form the 
lining of a gastrular sac, which attaches itself by the cells surrounding 
the mouth to some surface ; then the mouth closes ; a hyaline layer is seen 
between the two other cell-layers. An opening into the cavity appears 
at the free end, and the pores appear. The radial tubes are formed by 
evagination from the central cavity. Sometimes several larvae unite. 
The conclusion is that the Sponges are trilaminar, but have only two 
essential body layers. 
Time and place, &c., of reproductive processes as observed in 3 Calci- 
sponges and 4 Sibceous Sponges, given in tables, &c. ; MT. zool. Stat. 
Neap. i. p. 124, by R. Schmidtlein. 
Hermaphroditism observed in Sjpongelia cactos, Selenka (15). 
Surface mammae (14), p. 9, produce spiculated embryoes by budding, 
and ultimately develope oscula. 
W. S. Kent, Ann. N. H. (5) i. p. 1, considers the ciliated larvae of 
Sponges to be merely the results of fission. 
“ E. R. L.,’^ Nature, xviii. pp. 307 & 308, commenting on Keller’s paper 
(9), notices [the granular condition under which chlorophyll occurs in 
Spongilla ; and the difficulty of tracing the sponge embryo from the stage 
with two hemispheres of differently-sized cells to the bilaminate sac. 
(11). The Protozoan, i.e. Flagellate-Infusorian, theory of the affinity 
of Sponges is argued by detailed comparison of different stages and parts 
of different Sponges, with stages of various Flagellata. The ovum is a 
metamorphosed collar-cell. The embryo is not bilamellar, and its cells 
do not constitute a tissue. 
As parasites of Sponges are enumerated (3) — Amphipod Crustaceans ; 
Balauoid Cirrhipedia \ sessile Actinozoa^ 4 kinds, found on the surface ; 
