136 



SEA-UKCHIN. 



comes before our notice, the Common Sea-egg or 

 Sea-urchin (Echinus sphcere), whose external ap- 

 pearance is shown on plate l, fig. 2. There does 

 seem to be some slight connexion between the 

 three star-fishes which we have just examined; 

 but that there should be any connexion at all, 

 or any relationship, between the brittle-star and 

 the sea-urchin, appears too preposterous an asser- 

 tion for credibility : yet such is really the case, 

 as will soon be seen. The specimen from which 

 the drawing was made is a tolerably perfect one, 

 being still furnished with its array of spines from 

 which it derives its name of sea-urchin, the urchin 

 being a popular name for the hedge-hog. But if 

 these spines are rubbed away, a smooth surface 

 will be left, on which are numerous tubercles, 

 marking the spots on which the spines formerly 

 rested. If now the reader will take a damaged 

 urchin, plenty of which are to be found on the 

 shores, and examine its external appearance, he 

 will see that it has a very close relationship 

 indeed with the star-fishes. Let a common five- 

 finger star-fish be laid on its back, and the points 

 of its rays stitched round a little disc of leather, 

 it will then assume very much the aspect of a 

 skeleton urchin. Let then the spaces between 

 the rays be filled up with a substance of the same 



