OF STARFISHES. 183 



the length of a tree, we mean along a line drawn from one end 

 towards the other; but if now one were to cut across the trunk 

 and take out a transverse slice as thin as a wafer, it would seem 

 almost-absurd to speak of the length of the slice, meaning its 

 thickness; but yet the term would appear perfectly justifiable 

 to any unprejudiced mind upon considering its relations to the 

 surrounding parts from which it was taken : and so it would be in 

 relation to the starfish. Its length is commonly called its thick- 

 ness ; but I could show you other starfishes which are nearly or 

 fully as long, or, commonly speaking, as thick, as they are broad ; 

 and among the fossils certain mr 



starfishes (figs. 112, 113) which, 

 when alive, were attached to 

 stems, and whose bodies were 

 much longer than broad ; and 

 yet, in a view from the mouth 



Fig. 113. 



end, (fig. 112,) you might think 

 you were looking at one of the living starfishes, foreshortened 

 by the plastic hand of Nature. 



I now refer you to this side view (fig. 114) of the Trepang, 

 and then to its foreshortened aspect (fig. 115), which may be 

 compared to the thin, transverse slice from the tree, and ask you 

 if it were possible to discover its length in any other way than 

 along the line of vision, that is, right through what I might call 

 the thickness of this figure? 



We will, then, survey the interior of the starfish as if we 

 were looking into the mouth of a short tube and saw five groups 



Fig. 112. Pentatremiles florealis. Say. Natural size. A foreshortened 

 view of the anterior face, a, the median arm ; b, e, the two left arms ; c. d, the 

 two right arms ; f, the region between the arms formed by their lateral conjunc- 

 tion ; m, the mouth; r, the right and left openings of the reproductive organs ; r 1 , 

 the cloacal cavity, forming the common point of opening for the posterior end 

 of the intestine and a part of the reproductive organs. Original. 



Fig. 113. The same as fig. 112, in profile, as seen from above, a, the me- 

 dian arm ; a 1 , end of a ; c, c 1 , the right, and 6, 6 1 , the left arms ; /, the same as 

 in fig. 112 ; s, the posterior end of the body, where the stem is attached ; m and 

 r as in fig. 112. Original. 



