44 



give off narrower canals at about right angles. Some of the latter ramify and communicate 

 with mastichorions x ) ; others run deeper into the sponge, leading to a second system of wider 

 canals, parallel to the surface. (This process may even happen once more). From this second 

 (or third) system of reservoirs, which often winds itself like a serpent through the deeper parts 

 of the sponge, again narrower canals start which do or do not ramify and which are surrounded 

 by mastichorions, with which they communicate. On the other hand the mastichorions open 

 with wide apopylae in other canals, which so to say interdigitate with the former (PI. VI, figs. 

 i and 2). The system, consequently, is eurypylous. The excurrent canals unite and form larger 

 canals, from which numerous smaller ones start and fmally end at the sponge surface with 

 procts, which have about the same size as the stomata. The canals are distinctly lined with 

 pinacocytes; on the external sponge surface, however, I could not find undoubted cells, but in 

 many places I saw something like a cuticula. The parenchyma of the sponge represents a tissue 

 which in many respects resembles the so-called reticular or lymphoid connective tissue. In this 

 tissue with the many efferent and afferent canals are situated the mastichorions, which form 

 characteristic groups of various size (PI. VI, fig. 1). The whole area where these groups of 

 mastichorions occur, i. e. the choanosome is marked off from the ectosome by an undulating 

 line. In places of the choanosome where few mastichorions occur and in the ectosome the whole 

 tissue is less stained, which is due to the greater distance of the cells. Of these we find a 

 great diversity: close under the peripheral crust of spinispirae fusiform cells prevail, situated 

 with their long axis parallel to the sponge surface. In the second place we find comparatively 

 large cells, each with a large vacuole (PI. VI, fig. 3); then a quantity of scleroblasts of various 

 size, containing spinispirae in different stages of development (PI. VI, fig. 4). In addition there 

 are amoeboid cells etc. The tissue of the ectosome is continued around the vertical bundies of 

 tylostyles. Only it contains less cells, in fact chiefly fusiform cells with their long axis parallel 

 to the bundies and probably also connective tissue fibres. From the base of the sponge crust 

 bundies of tylostyles start and run almost perpendicularly; they sometimes branch dichotomously. 

 Towards the periphery they diverge and form conical brushes or tufts, slightly projecting beyond 

 the sponge surface. In addition we find a few tylostyles in tangential direction or irregularly 

 dispersed. In the main bundies almost all the apices look towards the periphery. The bulk 

 of large and minute spinispirae forms a superficial crust (PI. VI, fig. 1); but throughout the 

 whole parenchyma they may be found, sometimes again more profusely at the base, i. e. where 

 the sponge touches its substratum. The spicules are kept together in bundies by a periapt 2 ). 

 In some places it seems that the spicules are kept together by a deeply straining homogeneous 

 substance which I will call spongine, although it must not be forgotten that all so called sub- 

 stances are certainly not identical. It often gives the impression as if a layer of spongine covers 

 the substratum from which layer short perpendicular lamellae are given off; in some of these 

 spicules are imbedded and form an irregular network at the base of the sponge. This layer 

 should then correspond with the layer Keller described (1891, a p. 323) for Spirastrella 

 decumbens. 



i) I902 (2) VOSMAER & VERNHOUT p. 4. 



2) 1905 (<*) Vosmaer & Wijsman p. 23. 



