ECHINODERMATA. 181 



ion to which they belong, the dominant character of the animal 

 kingdom, bi/aterality, is as clearly laid down as in any of the 

 higher types ; and at the same time the upper and lower sides 

 are indicated to that extent and to that degree of specialization 

 which will not allow of a symmetrical bipartition of the body 

 in any other way than that which I have explained to you. I 

 would also mention, in passing, that, in the most remote geologi- 

 cal ages, the earliest corals that appeared on earth were as dis- 

 tinctly characterized by a right and a left and a front and a back 

 as are those of the present day. 



As I shall have occasion hereafter to speak of the next higher 

 class, to which the jelly-fish, (fig. 37,) sea-blubber, hydra, (fig. 27,) 

 &c., belong, I will pass over it now, and also another closely 

 related class, and lay before you the organic relations of the 

 Echinoderms, the fourth and highest group of this division. 



Echinodermata. I have selected for illustration two of the 



Fig. 109. 



umm 



Fig. 110. 



most widely diverse exemplifications of the lateral repetitive type 



Fig. 109. Asteracanthion rubens. M. and Tr. The common Starfish. One 

 fourth natural size. A view of the posterior face, m, the madreporifbrm body. 

 A line drawn through A, to the madreporiform body (rw), divides the body into 

 right and left halves. Original. 



Fig. 110. A semi-profile view of fig. 109, as seen when creeping up the per- 

 pendicular face of a rock by means of its tube-like feet, or suckers. A, the 

 median arm ; B, D, the arms of one side. Original. 



