144 ECHINID.E. 



that it is with their spines the Echini move themselves, 

 seize their prey, and bring it to their months, by turning 

 the rays of their lower edge in different directions. But 

 the correction of an error respecting the functions of the 

 ambulacra! tubes does not solve the problem relating to their 

 nature and use. This problem we are yet unable to solve, 

 as we know nothing more respecting them than that they 

 are connected with the aquiferous system.'" 



There can be little doubt that in all the Echinoderms 

 provided with these suckers, they serve not merely for 

 progression ; the lower we descend in the scale of animal 

 nature (and equally in the vegetable kingdom), the more 

 functions do we find performed by one organ. But observe 

 a living Starfish, or a living Holothuria, and see what 

 effective organs of progression these soft, flexible, weak- 

 looking tubes are. I have seen an Echinus miliaris, a 

 Spatangus purpureus, and an Amphidotus roseus all walk 

 along the bottom and up the sides of a dish of salt water 

 by means of their inferior tentacula ; and the first men- 

 tioned anchored itself by extending and bending its superior 

 suckers, so as to reach the bottom of the dish. In the 

 Sea-Urchins they are of a similar structure, and the ar- 

 gument against their being organs of motion, founded on 

 their position above as well as below, would equally apply 

 to the spines, to which organs the distinguished naturalist 

 of Switzerland has attributed all progressive powers in 

 these animals. 



The Sea-Urchins, as far as we know, are free throughout 

 their existence. In some of the genera we find a madre- 

 poriform tubercle or nucleus resembling that of the As- 

 teriadse, but there is no internal column attached. This 

 nucleus is very large in the embryo Urchin, and is placed 

 on one of the ovarian plates, all of which form a large 



