A. General. 2. Histology. 5 



sometimes not. In C. loricata they show a double contour. The sterrasters 

 in G. conchilega probably arise from cells resembling >sogenannten amoboideu 

 Wanderzellen in the transpai'ent zone below the zone of sterrasters, not from the 

 granular cells immediately beneath it. In G . cydomum massive cells in the pulp 

 with concretions are probably silicoblasts, the nucleus is always nucleolate, it is 

 gradually enveloped by the concretions. In C. vulcani pulp-cells containing such a 

 sphere with radial periphery are to be regarded as sterraster mother-cells [cf. 

 infra p 8 Vosmaer ( 2 )]. In A. cerebrum an efferent canal is surrounded by clear 

 tissue in a fibrous sheath. In the clear zone are radiating cells (gland-cells or 

 possibly epithelial cells) and spherical cells with stellate concretions, probably 

 aster mother-cells. In the afferent chones of G. cydonium the oxyasters lie as a 

 sort of filter, among them in the lumen are spherical or columnar cells, which may 

 be protective phagocytes. In the chones of A. mucronata a thick lining of radia- 

 ting cells is surrounded by circular fibres ; near the sphincter there is a central 

 axis in the lumen with trabeculae radiating to the walls. - In Corticium cells of 

 the middle layer apply themselves round the flagellate chambers, producing 

 the appearance ascribed by Schulze to granules in the jelly. The collar-cells of 

 O. lobularis show a sharp division between highly stained bases and less stained 

 distal parts. Sollas's membrane was observed in Erylus and elsewhere, but is not 

 normal; it appears, with no flagella , in O. hardened in alcohol; collars are se- 

 parated and flagella present in the same sponge hardened in osmic acid. 



Bidder [see also Vosmaer ( 1 ), and Vosmaer & Pekelharing and cf. Bericht f. 

 1893 p 4 V. & P.] finds Sollas's membrane as figured by Sollas and Dendy 

 in most paraffin sections of Sycon compressum, associated with change of cell- form ; 

 it never is present in the living sponge, and is therefore artifact. In the living 

 AS', raphanus it is possibly a phenomenon of suffocation. 



Topsent ( (; ) does not find glandular cells with 3 or 4 pedicels under the epi- 

 thelium of Dendrilla cirsoides n., nor can he convince himself of the cilia shown 

 on the epithelium by Lendeufeld , wrnais on connait la tendance de cet auteur a 

 couvrir de cils tous les epitheliums . The spherule-cells of Reniera Jlctvescens 

 11. do not blacken with osmic acid, but turn violet with iodine. Halisarca 

 sputum n. , besides the vesicular cells so strangely supposed by Lendenfeld to be 

 vegetable [v. supra] , has a second sort of spherule cell containing reserve 

 material in round grains. 



Wilson in Esperella fibrexilis u. finds rounded or amoeboid mesoderm cells 

 with well-staining bodies passing insensibly into spindle cells with body scarcely 

 staining; the latter are abundant around pores and at bifurcations of canals. 

 Ectoderm and epithelioid lining of canals are formed of flat cells. - After 

 boiling in caustic potash some of the oxytylote spicules always have the head 

 split into (three?) points. In the larva the bow-shaped spicules always show a 

 nucleated mass of protoplasm in the concavity , a similar structure is sometimes 

 found on the oxytylotes. 



Masterman( 1 ) fed Grantia compressa for 2 minutes, killing in osmic acid after 

 various periods in clear water. The choanocytes were well charged with carmine, 

 a few particles being in endodermal pinacocytes. Choanocytes were free from 

 carmine after 12 minutes, they undergo amoeboid transformation and migrate into 

 the mesoderm; probably excretory matters are removed by mesoderm cells or 

 metamorphosed choanocytes leaving the sponge through the ectodermal surface. 

 Masterman ( 2 ) compares these with Bidder's results. - - See also Griffiths. 



