14 Spong. 
XVII. SPONGER. 
in which the axis is a line drawn on a circular cylinder, and /3-spiraxons, 
in which the axis is a line drawn on an elliptic cylinder: the a-spiraxons 
include:—(1) the sigmaspira , pp. 3-5, (2) the spirula, p. 5, (3) the spini- 
spira , pp. 5-7, (4) the microspira , pp. 7 & 8, and (5) the sterrospira , p. 8 : 
the /3-spiraxons include:—(1) the sigma , pp. 8 & 9, (2) the chela , p. 9, 
(3) the diancistra , p. 9; Vosmaer (65).—The name “commata” proposed 
for small comma-shaped styli which apparently occur in all species of 
Desmacella , p. 89 ; diancistra, development and varieties of, pp. 102 & 103; 
Lundbeck (38). 
(d) Skeletal Anatomy.—Skeletal anatomy of Sycon compression 
[Grantia compressa\ Halichondrici panicea ,, and Suberites clomuncula, in 
relation to their conditions of life; Bidder (4). 
(v) Histology. 
(a) General Accounts.—H aller (17) pp. 69-75.—General ac¬ 
count of sponge histology; “ muscles and nerves are not developed in the 
tissues of sponges;” Goette (16) pp. 96 & 97.—Recent discoveries in 
sponge histology; Minchin (42) pp. 812 & 813.—General histology of 
Sycon raphanus, pp. 253-261, figg. 288-293; of Oscarella lobular is, pp. 262 
-264, fig. 294; of Chondrosia reniformis, and other forms, pp. 264-272, 
figg. 295-300: Schneider (54). 
(b) Histology of Special Organs or Classes of Cells.— 
Collar-cells of Sycandra raphanus ; Cotte (8), vide ii, c, ii.—Collar-cells of 
Rhabdodermella nuttingi n. sp., connected by basal processes; Urban (64) 
p. 273.—Sollas’s membrane in the flagellated chambers of Tetilla ridleyi; 
Sollas (58) p. 219. 
Cellules spheruleuses of Cliona vastifica; Cotte (7), vide ii, d, ii : 
of Phlceodictyon elongatum (Tops.), p. 61: of Gellius luriclus , n. sp., pp. 66 
& 67: of Gellius microtoxa, n. sp., p. 68: of Oceanapia robusta , p. 82: of 
Hamacantha implicans , n. sp., p. 107; Lundbeck (38). 
Peculiar vesiculate tissue in Halichondria (?) difficilis , n. sp.; Lund¬ 
beck (38) p. 30. 
(vi) The Germ-Layer Question. 
Sponges regarded as composed of ectoderm, endoderm, and mesoderm; 
Haller (17) pp. 63 & 64.—The gastral layer of sponges compared with 
the ectoderm, the dermal with the endoderm, of other Metazoa [vide ii, 
a, ii]; Lameere (30). — Homologies of germ-layers discussed; Minchin 
(42) pp. 812 & 813. 
C. Physiology. 
(i) General Accounts. —Vacant. 
(ii) Nutrition. —On the mechanism of absorption of food-particles 
by the collar-cells of Sycandra raphanus : the movements of the flagella 
in the flagellated chambers cause suspended particles to be driven against 
the walls of the chambers, thus giving rise to phenomena of thigmotaxy. 
Experiments show that the collar-cells can ingest grains (of starch) of a 
bulk exceeding that of the cell itself. When such a grain touches a 
collar-cell, the latter adheres to it, and sends creeping pseudopodial 
expansions over it, until the protoplasm of the cell is moulded on the 
foreign body, and is reduced to a thin layer completely or partially in¬ 
vesting it. The collar disappears during these changes. Ingestion can 
