192 



THE ORGANIZATION 



achal region of the intestine, and terminates (at A 1 ) close to, and 

 in the same line with, the madreporic canal. 



The reproductive organ consists of a thick tube (o to ov) which 

 at one end opens on the mid-line of the back, through a slightly 

 raised protuberance (o) immediately over the madreporic canal, 

 and at the opposite end forks into a dozen or fifteen tubules, (fig. 

 114, ov 1 , ov 2 , fig. 115, ov'*, ov*,) that spread themselves right and 

 left among the intestinal folds and the ramifications of the re- 

 spiratory branches. 



Mark the contrast now between these two foreshortened 

 views; the Starfish (fig. Ill) exemplifying the perfection of the 

 type in a multiplied sameness, and the Trepang (fig. 115) set- 

 ting forth the subordination of the type to the bilateral domi- 

 nant, by the culmination of the reducing process which has 

 established single organs or pairs of organs, at or on the right 

 and left of a median line. The pair of respiratory appendages 

 (r^ 1 ) of the latter are multiplied in another form (fig. HI, stf 1 ) 

 five times in the former. The reduction of the rows of external 



Fig. 117. 



Fig. 117. Psolus phantapus. Strfldt. ^ natural size. From a specimen 

 caught in Massachusetts Bay, and kept in the Aquarial Gardens, at Boston. 



