24 HOLASCUS EDWARDSII. 



The rare styles and tylostyles of the root-tuft, which, as above stated, may 

 be foreign to the sponge, are covered with spines, and near the distal, rounded 

 end 12-17 n thick. The distal end itself is either simply rounded off or, more 

 frequently, thickened to a terminal tyle, with a maximum transverse diameter 

 of 32 M. 



The anchoring spicules (Plate 20, figs. 5-20) are anisoactine rhabds. I 

 did not observe any long intact ones. The longest fragments observed were 

 45 mm. in length. The morphological centre, the position of which is clearly 

 marked by a well-developed axial cross (Plate 20, figs. 5-8a) is only 137-200 m 

 distant from the distal end of the spicule. Thus, whilst the proximal ray may 

 attain a length of over 40 mm., the distal ray is usually less than 0.2 mm. long. 

 Proximally the spicule is gradually attenuated to a fine point. Distally it 

 thickens, and it attains its maximum thickness some distance beyond the middle 

 of its length, long before the morphological centre (axial cross) is reached. 

 Beyond, it again becomes thinner, and near the distal end, at the thinnest point 

 between the morphological centre and the terminal anchor, is 7-11 m thick, 

 about two thirds to three quarters of what it measures in the middle. At the 

 distal end the spicule is thickened to a terminal tyle. 



The proximal part of the spicule (Plate 20, fig. 11) is perfectly smooth. 

 Somewhere about the middle of its oblique length, backwardly directed spines 

 begin to make their appearance; these usually enclose an angle of 20-30° with 

 the axis of the spicule. At first (Plate 20, fig. 12) these spines are very small 

 and far between. Farther on (Plate 20, figs. 13, 14) they become larger and 

 more numerous, and they continue to increase in number and size quite up to 

 the morphological centre (axial cross). On the distal ray the spicule has four 

 to seven spines every 100 ^ (Plate 20, figs. 5-10, 15-20). In the middle of the 

 spicule the spines are uniformly scattered and not arranged in groups (Plate 20, 

 figs. 13, 14). Towards the distal end they tend to form verticillate clusters 

 (Plate 20, figs. 5-8, 15-20), two of which are particularly pronounced, one situ- 

 ated at the morphological centre (axial cross) (Plate 20, figs. 5-8a), the other 

 at the end. Together with the terminal tyle this second cluster of spines forms 

 the anchor. 



The large spines of the distal part of the spicule are 10-30 m long and 4-7 yu 

 thick at the base. The terminal ones, which form the anchor-teeth, are similar 

 to the others, but somewhat stouter. 



The anchor appears as a conspicuous terminal thickening with an outline 

 closely resembling an inverted gothic arch. From the proximal side of this 



