PORIFERA. II. 



8 9 



obvious conclusion that the}- are excurrent canals; if so, we should expect to find oscula at the points 

 of the branches. It may, however, also be possible that among the mentioned pores some may act as 

 incurring openings, others as excurrent ones. 



The skeleton is chiefly constructed as in the preceding species. It consists in stem and branches 

 of a powerful axis which is also here somewhat spirally twisted, especially in its lower part. The 

 lateral branches are formed in the common way. The skeleton of the branchlets is formed by a fibre 

 more or less long according to the length of the branchlets; in the long branchlets the fibres are out- 

 wardly very fine, and outermost they have only quite few spicules. The fibres of the branchlets are 

 inserted in the axis in the common way. As the branchlets are arranged more or less circularly, their 

 fibres, in a transverse section passing through a circle of branchlets, are 

 all seen to go to the middle of the axis like the spokes of a wheel. 

 When the layer of tissue with the branchlets and their fibres is 

 removed, so that only the axis is left, this is seen to be transversely 

 striated on account of the circular arrangement of the branchlets, the 

 part of their fibres that is inserted in the axis appearing as darker circles 

 when the other part is removed. The axes of the branches continue through 

 the middle of the swollen terminal part, and at the outer end they spread 

 in a somewhat peuicillate way. From the part of the axis running through 

 the terminal knob rather regular, thin fibres issue to the surface, through 

 which their outer ends project quite slightly (Woodcut fig. 3). Thus 

 the whole terminal knob may be regarded as a collection of coalesced 

 branchlets. Between the mentioned fibres in the terminal knob are 

 moreover found some scattered spicules. In the above mentioned places 

 of the stem and the branches where no branchlets are found, fibres are 

 nevertheless found as in the other places, inserted in the axis in the 

 same way, and these fibres continue into the layer of tissue, which is, 

 besides, highly filled with spicules some of which are running chiefly 

 longitudinally, while most of them are situated irregularly. Some of 

 these spicules project a little through the surface. In these places the 



layer coating the axis is of greater thickness, so that it may more likely be regarded, as if the branch- 

 lets were coalesced to one layer. In the layer of tissue which coats the other part of the axis, spicules 

 are found rather copiously of which some are running longitudinally, while a great part are irregularly 

 scattered; the dermal membrane is supported by the outermost ones of these spicules. Where the 

 branchlets are long there are the fewest spicules in the layer of tissue; the shorter the branchlets are, 

 the more spicules are found in the layer of tissue, and the greatest number of spicules are found 

 where the branchlets are quite wanting. In the stems and branches the needles of the axes are 

 cemented by a clear mass of spongin, giving to the axes a slightly yellowish colour. 



Spicula: a. Megasclera are styli, straight or almost straight; they are fusiform, tapering evenly 

 towards the rounded end, and towards the point to about the same degree; therefore the point itself 

 is short, but it may be more or less blunt and is sometimes rounded. There is no distinct difference 



The Ingolf-Expedition. IV. 2. 12 



Fig. 3. Cladorhha ienuisigma 



n. sp. 



Longitudinal section through the 



end-swelling of a branch showing 



the skeleton, x 10. 



- 



