PORIFKRA. II. 95 



directed issue from this axis in the same way as in the preceding species. These axes run through 

 the middle of the short lateral branches before mentioned, and accordingly they attain only a rather 

 small length. Fibres issue from the axes of the stem and the branches, quite corresponding to the 

 fibres of the branchlets in the preceding species. They issue all round, and most frequently they are 

 arranged in a more or less circular way, and they are inserted in the axes in the common manner, so 

 that in a transverse section they are seen to meet in the middle (Woodcut fig. 5). The circular arrange- 

 ment cannot be seen in the exterior, but when the layer of tissue is separated from the axes, a ringlike 

 structure is seen in these, owing to the basal parts of the small axes, which are inserted into the axis 

 (PI. Ill, fig. 8). Now the only difference between this species and the preceding ones is that while in 

 these the fibres inserted in the axes support free branchlets, they support in the present species the 

 coherent part of tissue on the stems and branches, continuing from 

 the axis out through this tissue, and their ends projecting a little. 

 These fibres are in this species of about the same thickness through- 

 out their length; sometimes they are a little curved. They may be 

 somewhat branched, especially in their outer part, so that the number 

 of projecting ends is greater than the number of fibres inserted in 

 the axis. The part of the sponge coating the stem and the lateral 

 branches and supported by the mentioned small fibres is not solid, 

 but is, as before mentioned, pierced by a coherent system of cavities. 

 A row of cavities is especially found inmost, round the axis, arranged 

 like stories above each other, separated by the almost plate-shaped 

 parts of tissue in which the small fibres run, but still connected 

 with each other. Accordingly, a longitudinal section of the sponge 



reminds strikingly of the chambered root-stock of Cicuta virosa 



& ' Cart. 



(PI. Ill, fig. 9). In the outer part of the layer of tissue the cavities A piece of a transverse section showing 



are more canal-shaped, and they open everywhere on the outside tte axis and * e ^all fibres, m the 

 * tissue embryos are seen, x 7. 



with round or roundish openings between the projecting ends of 



the fibres; their being at the same time connected with each other gives rise to the mentioned netlike 

 structure. A comparison with the other species of the genus and especially the correspondence in the 

 skeletal structure imparts the impression that the sponge-body coating the axes must be regarded as 

 having arisen by a coalescing of branchlets, or must, at all events, be corresponding to coalesced 

 branchlets, and that the mentioned system of cavities and canals, therefore, does not belong to the 

 canal system proper, but is a secondary formation. This is also indicated by the fact that the cavities 

 are abundantly connected with each other, so that one cavity in the sponge opens on the surface by 

 several ways and to different sides. Whether free branchlets are found at any time during the growth 

 of the sponge, and whether a real coalescing takes place, or the mentioned structure appears from the 

 beginning, I am not able to decide, as I have had no young individuals 1 !. The described regular 



"I I have later seen a specimen which was surely a rather young one, and as it showed partly free branchlets, 

 which were chiefly connected oniy near the axis, this seems to indicate that the above described condition develops during 

 the growth of the individual. 



