122 = A. OKA. 



Closer examination shows that what appeared as a distinctly 

 reticuinted marginal area is a sort of broad rim around a cliitinous 

 body of compact nature. This rim consists of a nundoer of prismatic 

 caskets filled with gas, the diameter of the caskets increasing as we 

 approach the margin. The hollow caskets have their axis vertical to 

 the plane of tlie statoblast and are arranged in two horizontal lasers. 

 They serve as a buoy to float the central body, which is the most 

 important part of the statoblast. 



If the free edge of this rim, or the annulus as it is called, be 

 examined under a strong power, we see a great number of minnte 

 hooks projecting from it (fig, 35, VI. XIX). They are found most 

 abundantly where the margin is somewhat angular. Soine of them 

 are complex, while others are simpler, but all are fijrmed by the 

 combination of simple hooks in various ways. They are mere out- 

 li'rowths of the ed^'e of the annulus, and have no direct connection 

 with the central body, as is the case in Cristatdla and Pect, 

 magnißcd. They are short and stout, and the tips are rounded. 

 They measure about 0.02-0.03 mm. in length and are too minute to 

 be of much functional importance. When the annulus splits hori- 

 zontally, as it does of itself when the polypide begins to develope within, 

 these, spine.5 are found onl}' on the margin of the concave side. 



The curvature <jf the annulus and the presence of hooks on the 

 free edge seem to be worth carefid consideration. In :dl statoblasts, 

 tlie annulus serving as buoy p)erforms an eiiectual service in dis- 

 tributing the species as well as in enabling the establishment of 

 colonies near the surface of water. Where the annulus shows 

 curvature, the distributive power is evidently enhanced, ex- 

 posing its curved surface to the influence of the motion of water, 

 or, if dried up, of wind. As to the hooks I have no doubt thîit, 

 as Kraepelin has said, they serve as anchors to secure attachment for 



