12 AMONG THE SEA-URCHINS. 



shell. The animal has command over each distinct spine, etc., 

 either individually or as a whole, the prick of a needle bringing all 

 the spines and pedicellaria, or nippers (Fig. i, F), around the 

 cause of irritation ; while, if placed on a table, and a lighted 

 match be held near it, the spines will move the entire body as 

 rapidly as possible, away from it. 



By various most interesting experiments Professor Romanes 

 satisfactorily proved the existence of a nerve plexus in the 

 organised membrane, which, in a tissue of exceeding thinness, 

 passes between the sutures, where the plates come in contact with 

 each other. Thus the animal within the shell has full command 

 of the situation, although distinct independent action appears to 

 be possessed by the pedicellaria and minute organs of touch dis- 

 tributed about the shell, especially some near the mouth, with 

 tiny heads covered with cilia, which Loven supposes to be organs 

 of taste. 



The summit of the shell shown at Fig. i, C, gives at p the 

 membrane surrounding the anus, around which are the five 

 "genital" plates,^-.; one of these, larger than the others, supports a 

 spongy tubercle, perforated by many minute pores (Fig. i, C, in). 

 This is the madreporic filter, by which the internal canals are kept 

 supplied with the purest sea-water. Wedged between the genital 

 plates are five smaller ones, long known as the " ocular " plates, 

 shown at o, each of which can protrude from a small hole therein a 

 curious little tentacle or feeler. The enquiry into the properties 

 of this organ of sense has caused a large amount of diverse 

 opinion, especially as to its possessing at its base an eye-spot, or 

 organ of vision, which is now doubted by the highest authorities. 



We very seldom found an Echinus left out of water by the 

 receding tide, but sometimes this was the case, as we found during 

 a visit to the rocks of Dalby, where that storm-beaten and 

 dangerous reef, or headland — " the Niarbyl"- — runs out to sea for 

 so many hundred yards. We were boating and dredging around 

 this point in deep water several times when there was a calm sea, 

 our hunting being most successful round its precipitous sides. 

 There, at low water, were most lovely Anemones of many varieties, 

 disporting themselves in all their gorgeous beauty and wealth of 

 tentacle, while amongst the crevices we now and then found an 



