49 



towards the pointed end. The four tangential rays which lie just below the 

 dermal membrane are also smooth, pointed, gradually attenuated and about 

 200 M long. 



The stout hypogastralia -which lie opposite the hypodermalia are in many 

 respects similar to the latter but difPer from them considerably by their proximal 

 rays being much longer (350 /^ and more) and usually of a different shape. 

 These rays are spined and protrude freely into the gastral cavity. At the points 

 of egress they raise the gastral wall to form slender, conical protuberances. 

 The whole of the proximal ray is covered with vertical' spines and there is gener- 

 ally no spindle-shaped thickening in its central part. Like the other five 

 smooth rays of the spicule it is gradually attenuated towards the sharp-pointed 

 end. 



In the lower part of the specimen basal anchor-spicules are met with here 

 and there, between the longitudinal rays of the principalia which form the 

 supporting skeleton-net. Although pretty slender these spicules are inflated at 

 the distal end, club-shaped, and emit from the terminal thickening a verticil 

 of a varying number, often three oblique and recurved anchor-teeth. These 

 teeth contain no axial threads and are therefore not to be considered as 

 rays but as mere spines. The axial cross does not lie in the terminal thicken- 

 ing near the place of insertion of these teeth, but higher up in the shaft (pi. 

 IX, f. 6). 



Four different kinds of intermediary parenchymalia are to be distinguished : 

 slender oxyhexasters ; stout-rayed micro-oxyhexactines, the rays of which show 

 a tendency to bifurcation so that they pass intft oxyhexasters ; graphiohexasters 

 or, as I now prefer to designate them, graphiocoms ; and calicocoms. 



The slender oxyhexasters are abundant in the walls of the incurrent system. 

 They have short main-rays which are not thick, and terminally bear three or 

 more thin, straight or slightly curved branch-rays (pi. IX, f. 5). 



The oxyhexactines and the stout oxyhexasters they pass into, are restricted 

 to the walls of the excurrent system. They have remai^kably thick, conic rays 

 and measure 100-150 /^ in diameter (pi. IX, f. 2-4). 



The graphiocoms are not very frequent and chiefly met with in the 

 subdermal region. In my preparations the branch-rays forming the long ter- 

 minal brushes are generally broken off, so that one usually sees only the six- 

 rayed cross formed by the main-rays with their terminal discs which bear on the 

 convex outer surface numerous stumps of the branch-rays which have been 

 broken off (pi. IX, f, 7a). Usually one finds in the vicinity of these the long 

 slender, straight, raphid-like branch-rays, either still joined in brushes, or 

 isolated and scattered. 

 7 



