VIIl] 



THE PARTITIONING OF SPACE 



391 



case, are comparatively few and irregular in the earlier stages of 

 Heterophyllia, though they begin to appear in numbers after the 

 main, more or less radial, partitions have become numerous, and 

 when accordingly these radiating partitions come to bound narrow 

 and almost parallel-sided interspaces ; then it is that the transverse 

 or periclinal partitions begin to come in, and form what the student 

 of the Coelenterata calls the "dissepiments" of the coral. We 

 need go no further into the configuration and anatomy of the 

 corals ; but it seems to me beyond a doubt that the whole question 

 of the complicated arrangement of septa and dissepiments through- 

 out the group (including the curious vesicular or bubble-like 

 tissue of the Cyathophyllidae and the general structural plan of 



Diagrammatic section of a Ctenophore {Eucharis). 



the Tetracoralla, such as Streptoplasma and its allies) is well 

 worth investigation from the physical and mathematical point of 

 view, after the fashion which is here slightly adumbrated. 



The method of dividing a circular, or spherical, system into 

 eight parts, equal as to their areas but unequal in their peripheral 

 boundaries, is probably of wide biological application ; that is to 

 say, without necessarily supposing it to be rigorously followed, the 

 typical configuration which it yields seems to recur again and 

 again, with more or less approximation to precision, and under 

 widely different circumstances. I am inclined to think, for instance, 

 that the unequal division of the surface of a Ctenophore by its 



