56 



arranged crosswise, vertical to each other, much shorter than the main-ray but 

 very stout and gradually attenuated to the pointed end. They are strongly 

 curved, the two pairs of opposite ones forming semicircular bows, the concavity of 

 which is directed shaftwards. It is to be remarked that both the main ray and 

 the four lateral rays forming the anchor-teeth, which arise from the main-ray 

 with trumpet-shaped extensions, are traversed by axial threads throughout their 

 entire length (pi. X, f. 12). 



The basalia of the second kind are diactines. They have the appearance of 

 a long shaft, pointed at the upper end, which is however not so thick as the main- 

 ray of the pentactine anchors. With the exception of the distal end, the shaft 

 is covered in its entire length with slightly curved spines, directed backwards 

 (upwards). The distal (lower) end is thickened and club-shaped. From the 

 equator of this terminal inflation a verticil of 6-10 spade-like teeth which are 

 bent upwards, arise (pi. X, f. 13). These teeth have nothing to do with rays; 

 they are mere spines, comparable to the thorns projecting in great numbers 

 from the upper part of the shaft. That it is so, is shown not only by their simi- 

 larity with the latter but also, and still more clearly, by the variability of their 

 number, by the absence of axial threads and particularly by the fact that the axial 

 cross of the central canal of the shaft usually does not lie in the terminal inflation 

 from which they arise but higher up in that portion of the shaft which is free 

 from spines. Sometimes a slight swelling indicates the position of the axial 

 cross : that is the centre of the spicule. In the terminal inflation the central 

 canal dissolves itself into a bush of short terminal branches. 



Having now described the adult sponge I will give the results of a compari- 

 son of those structures of the differently aged specimens at my disposal, which 

 are of interest in studying its post-embryonic developement. 



In the external shape of the entire sponge only very slight differences are 

 to be discerned between differently aged individuals. The smallest specimens 

 differ from the larger ones chiefly in their being on the whole more slender. The 

 ratio of breadth and length (exclusive of the root-tuft) is in the smallest speci- 

 men 1: 6, in the largest one, preserved in its entire length, 1:5. It appears 

 probable however that still larger specimens again revert to a breadth- and length- 

 ratio similar to that of the smallest ones. As in EnpledeUa oiceni, the larger 

 specimens have an oval (ratio of axes 3 : 5) and not a circular transverse section. 

 The small specimens at my disposal, on the other hand, have a circular and not 

 an oval transverse section. 



I took particular interest in the arrangement of the spicular fibres in the 

 main skeleton-net of differently aged specimens because I hoped, by studying it, 

 to gain an insight into the mode of growth of the sponge. 



As was to be expected, the corresponding priucipalia are longer and thicker 

 in older than in younger specimens. They grow with the age of the sponge 



