REPORT OF THE DIRECTOR I9IO 221 



While this medium was becoming more viscid, bubbles continued to 

 rise, though at longer intervals. The figure shows a compound 

 bubble and a small new one just next to it, the aggregation not 

 having moved out of the field of view before the exposure was made. 

 Figure 2 of this plate also shows evidence for these canals, particu- 

 larly at the aborad ends of the two BB. 



In plate 6, figure i, we have evidence of a different character to 

 offer. This figure represents the area cut under to liberate the 

 specimen from its bed and the cutting was in a sense fortunate for, 

 although it removed all surface features and even the epithecal 

 canals themselves, it gave us some cross sections of the sutural canals 

 and to some of these we will give brief attention. 



Five millimeters to the left of the orad apex of post.B is a shaded 

 area crossing the suture at right angles. This seems to indicate the 

 former presence of an epithecal canal now cut away. Occupying this 

 shaded area is a circle 2.3 mm in diameter which is clearly out- 

 lined by the carbon black remains of its former organic walls. 

 Seven millimeters to the right of the orad angle of this basal is 

 another sutural ring of similar character, measuring 1.7 mm in 

 diameter and 5 mm to the right of this is an oval similarly out- 

 lined. This oval has a minor axis which measures 2 mm and a 

 major axis of 3.3 mm, the latter at right angles to the suture. Both 

 the specimen and the negatives show a much smaller ring on this 

 suture at a point 2 mm to the right of the upper angle of the 

 basal, but its position in a shadow effectually prevents its being 

 recognized in the figure. 



The carbon blackened rings, their position on the suture, their 

 distance from the apex of the plate, their distance from each 

 other, the position at a transverse shading, their diameters, and 

 the transverse position of the major axis of the oval; all indicate 

 these structures to be cross sections of cylindrical canals. The 

 oval is evidently a cross section made nearer the surface of the 

 plate or where the floor of the two wings of an exothecal canal 

 dipped down to make a junction with the sutural canal. In 

 other words, this is a cross section of a sutural basin hke that 

 already noted in plate 5, figure 4. The diameters of the rings last 

 measured (0.23, .17 and .2 mm) give an average a little larger 

 than that obtained from the measurements of the sutural canals of 

 Cliocrinus perforatus, but they are remarkably close to 

 the measurements of the papulae of the aquarium specimen of 

 Asterias forbesi. 



