Porifera. 



uocytcs, with retractile flagellum, amoeboid body and collar. They unite occa- 

 sionally by the borders of their collars, hence the mistaken belief in Sollas's mem 

 brane; (3) Colleucytes and Sarcencytes, = cellules digestives pigmenteesa 

 and cellules granuleuses du mesodenneu described in Mouaxouida, some of these 

 cells become reproductive elements; (4) cellules spheruleuses and vesicu- 

 leuses, = cystencytes, choudrencytes, thesocytes, and chromatocytes ; appearing 

 also in the ectosome and in general under all epithelial surfaces. For the diffe- 

 rent species many observations are given as to the granules contained in living 

 cells. Many Tetractinellids, as noted by Carter for Pilochrota, leave on the sur- 

 face of attachment a varnish-like deposit of brown granules. Scleroblasts are 

 for megascleres probably cellules granuleuses du rnesodernie; for rnicroscleres 

 probably as in Esperelliuae, where they originate in ordinary epithelial cells. In 

 Isops intuta the form and size of the vesicular cells suggest that they are mother- 

 cells to the sterrasters. It is noticeable that in P. mediterranea the anatriaeues 

 may develope a second circle of two or three branches below the principal 

 cladoine. No sensitive function has been demonstrated for aesthocy tes. 



Lendenfeld ( b ) [see Lendenfeldf 1 )] finds in Tetractinellida the epithelium only 

 exceptionally composed of mushroom-shaped cells as supposed by Minchin [whose 

 views are misrepresented, cf. Bericht for 1892 Porif. p 11] and Bidder [ibid, 

 pp. 8 10]; the gland-cells generally belong to the middle layer and have a flat 

 ectoderm outside them. The surface cells, however, are cylindrical in the Digi- 

 telleu of Oscarella lobularis (which are poison glands), the afferent canals of 

 Corticium, and the choual sphincters of Ancorina] glandular in the pore-canals of 

 Erylus discophorus - - vielleicht sind sie Epithelzellen , conical in the afferent 

 pores of Geodia conchilega rnoglicherweise Epithelzelleuc , multipolar and 

 pear-shaped on the canal-diaphragms in G. cydonium, radial and fibrous in the effe- 

 rent pore-canals of G. conchilega. Fusiform cells, apparently contractile, are con- 

 stantly met with : in the skin of the praeoscular chamber of Ancorina cerebrum, 

 in its chonal sphincters, and round the main canals [v. infra] ; particularly in the 

 choues of A. mucronata ; in the chones of Erylus discophorus, and the diaphragms 

 and afferent pores of G. conchilega, circularen Contractors and more numerous 

 wradialen Dilatores, which in the afferent pore-canals may be sensory; circular 

 in the chonal sphincters of G. cydonium] longitudinal sheathing the chones of 

 Caminus vulcani. The canal diaphragms of Er. discophorus are composed of flat 

 fusiform cells, without any division into epithelia [cf. Bericht f. 1892 Porif. 

 p 11 Minchin]. Die von Sollas als Asthocytes (Sinneszellen) beschriebeneu 

 Elemeute [cf. Exper. Untersuchungen u. 3. w. in: Zeit. Wiss. Z. 48. Bd. pG78, 

 line 13] were only recognised in G. conchilega. 0b das aber wirklich Siunes- 

 zelleu sind, scheint mir sehr fraglich. Fibrils connecting the sterrasters were 

 spindle-shaped and granular in G. cydonium and C. vulcani, staining with haeina- 

 toxylin-eosin ; in C. vulcani the granules closely resemble those in the brown, 

 multipolar cells outside the sterrasters, but in neither sponge were nuclei found 

 in the fibrils [cf. Bericht f. 1893 Porif. p 3 Topsent]. In G. cydonium in the 

 clear zone under the sterrasters are fibril bundles and multipolar cells, and also 

 mulberry-cells , whose yellow concretions give its colour to the sponge and are 

 to be considered as food -stores. In C. vulcani about the afferent system are 

 structureless lobed masses, up to 70 (j, diameter, staining with picrocarmine ; they 

 are possibly stored nutriment and possibly protective secretion. The vesicular 

 cells of Pachastrella, Caminella loricata, Ancorina cerebrum, and A. mucronata are 

 symbiotic algae, probably also in Oscarella] this is more doubtful for those of 

 Ecionemia, and the pigment-cells of Er. discophorus are only a modification of 

 spindle and stellate cells ; but in this species vesicular cells are sometimes present, 



