HOMOLOGIES. 215 



course, united at the base, then stripping it off 

 and spreading it out flat, we should have a five- 

 rayed star. But in thus dividing the broad zones 

 of the Sea-Urchin into halves, we leave the 

 narrow zones in their original relation to them, 

 except that every narrow zone, instead of be- 

 ing placed between two broad zones, has now 

 one half of each of the zones with which it 

 alternated in the Sea-Urchin on either side of 

 it, and lies between them. The adjoining wood- 

 cut represents a single ray of a Star-Fish, 



One arm of Star-Fish from the oral side. 



drawn from what we call its lower or oral side. 

 Along the centre of every such ray, diverging 

 from the central opening or the mouth, we have 

 a furrow, corresponding exactly to the narrower 



