10 Spong. 
XVJI. SPONGIiE. 
B. Morphology. 
(i) Genei'al Accounts. 
Organisation of Tetraxonia ; Lendenfeld (27), pp. 1-3, figg. 1-4. 
(ii) External Characters. 
Placosoma paradictyum n. g. n. ap., has tlio body-aurfacos differentiated 
into a front, without oscula, and a back, with numerous oacula ; Ijima (22) 
pp. 3-9. — Localisation of pigment in sponges ; Cotte (9) pp. 518-520. — 
Diverse modes of coloration in sponges, pp. 366 & 367, selection of little 
importance in determining the coloration, p. 438 ; Mandoul (33). 
(iii) Anatomy of the Soft Tissues. Canal-System , 
Remarks on the Canal-System of Sponges in general ; doubt is thrown 
upon the statements of Topsent [v. Zool. Rec. 1900, Sponges, pp. 4 & 15] 
with regard to the canal-system of Clionidce ; Cotte (9) pp. 424-436. — 
Canal-system and flagellated chambers of Leucopsacus orthodocus Ij. ; Ijima 
(22) pp. 40-42. — Structure of Prophysema haeckelii n. sp. ; Leon (29). 
(iv) Skeletal System. 
(a) General Accounts. — Vacant. 
(b) Material of the Skeleton. — Vacant. 
(c) Morphology, Development and Nomenclature of 
Skeletal Elements. — “ Tylfloricome ” for a floricome in which the 
terminals end in pin-head knobs ; Ijima (22) p. 52. — Application of the 
names Discohexactin and Discohexaster discussed ; Schulze (48) p. 9. — 
Spicule-forms of Tetraxonia ; Lendenfeld (27) pp. 4-13, figg. 6-44. — 
Structure and development of the pithed fibres of Haddonella topsenti 
n. g. n. sp. ; Sollas (49). 
(d) Skeletal Anatomy. — Of Lithonina ( Porosphcera , Plectinia n. g.) 
and Sestrostomella ; PoSta (36). — Of Tetraxonia ; Lendenfeld (27) pp. 
3 & 4, figg. 3-5. 
(v) Histology. 
(a) General Accounts. — Histology of Leucopsacus orthodocus Ij. ; 
Ijima (22), pp. 40-42. 
(b) Histology of Special Organs or Classes of Cells. — 
The flask-shaped form of the dermal epithelium in a calcareous sponge 
explained as due to secretory activity, representing perhaps the excretory 
organs of the sponge ; Urban (53). — Muscle-fibres of an undetermined 
calcareous sponge, study of their striation ; Prenant (40) p. 1042. 
Archaeocytes of Leucopsacus orthodocus Ij. ; Ijima (22) p. 41. — Celhdes 
sphdruleuses , their nature and function ; Cotte (9) pp. 533-548. — 
Central cells of the flagellated chamber, their nature and significance dis- 
cussed ; Cotte (9) pp. 430-432 : possible explanation of the central cell 
as a phagocyte migrated towards aerated water ; Cotte (10), p. 739. 
Alterations undergone by choanocytes when asphyxiated ; Cotte (10). 
Histology of the pithed fibres of lladdouella topsenti n. g. n. sp. ; Sollas 
(49). 
