LUCERNARIJ3 AND THEIR ALLIES. 



45 



young is positive so far as tlic relative age and position of the tentacles are con- 

 cerned, and the reader will not do amiss to consult the paragraph devoted to tlieir 

 elucidation, while following out the description of the adult forms. 



Cut 4. 



93. The resemblance of the accompanying diagram (cut 4) to a segment of a 

 honey-comb is obvious at a glance, not only in tlie relative position of tlie ten- 

 tacles, but also in the shape of the outline of their bases. The proportions in size, 

 however, are altogether different. Except on the periphery of a group, every 

 tentacle is surrounded by six or, perhaps, sometimes five others, and, as they are 

 all in contact, they naturally compress their bases into the polygonal forms wliich 

 we have exhibited in the diagram. Those on the periphery are rounded on the 

 free side, and consequently seem to prove that the many-sidedness of the others is 

 due to a mutual restriction of their limits. The asymmetry of the group may be well 

 expressed by comparing its outline to an anisosceles spherical triangle, projected on 

 a plane in such a way that its longest side is convex and the two others concave. 

 The longest side will then correspond to the distal border of the group, and the 

 next longer will trend along that border which faces towards a partition. Gene- 

 rally speaking, the oldest tentacles lie nearest the convex or distal side of the figure, 

 or rather, we might say, are embraced in the angle formed by the two longest sides; 

 and the site of new developments is near the shortest side, or verges in that direc- 

 tion. When, now, the tentacles appear to be in files one may observe that they all 

 diverge from about one point, and that that point is at the junction of the two 

 shortest sides of the triangle. Of course it will be seen that those in one row alter- 

 nate with those in the next on either side, and that, inasmuch as those on each side 

 of any one file fit into the intervals, and actually meet at their bases between the 

 succeeding tentacles of that file, a very slight divergence of two lateral rows may 

 bring the globose tips so nearly into exact line with those of the middle one as to 

 make them appear to form a perfect continuity. 



