ECHINODERMATA. 285 



eternally hidden from the eyes of man, sleeps under the heavy mass of 

 water; and yet man imagines that everything in Nature has been 

 created for his use and for his glory. 



M. Hupe records a somewhat curious observation in connection with 

 the spines, which serve as a means of defence to the Echinodermata. 

 He found a small mollusc, of the genus Stelifera, which had sought 

 shelter in Leixidaris imperialis, an urchin, native of Australia ; in a 

 word, the interior of one of these prickles had been hollowed and 

 enlarged so as to serve as a retreat for this improvised guest. 



What unexpected facts does the study of animals present ! Nature 

 has bestowed a protecting armour upon one little being ; another still 

 smaller animal discovers this, and places itself for shelter under the 

 protection of these levelled bayonets ! Numerous anecdotes are told 

 of them. Thus : a man ignorantly put into his mouth one of these 

 creatures, with all its prickles, and, being detected, thought himself, 

 in his pride, compelled to swallow it because he was being looked at ; 

 immediately his mouth was full of blood. The next day he was in 

 such a state of suffering that he could neither eat nor drinfi, and for a 

 long time his life could only be preserved by nourishing injections of 

 soup, cream, and rice. 



Now let us see by what organic mechanism the urchin contrives 

 to transport itself and walk. The tentacula, or suckers, are hollow 

 internally, and, as we have said, are provided with small muscles. By 

 the influx of liquid which they inclose they become inflated through- 

 out all their prickles, in such a manner that they can attach them- 

 selves to any solid body, at the will of the animal, by means of their 

 terminal suckers. Fredol, in " Le Monde de les Mers," thus explains 

 the urchin's mode of progression. "Let us imagine," he says, "one 

 of these creatures to be at rest ; all its spines are immovable, and, all 

 its filaments repose within the shell ; some of these involuntarily 

 escape ; they extend themselves and feel the ground all round them : 

 others follow, but the animal is firmly fixed. If it wishes for change 

 of place, the anterior filaments contract themselves, whilst the hinder 

 ones loosen their hold, and the shell is carried forward. The sea- 

 urchin can thus advance with ease, and even rapidity. During his 

 progression the suckers are only slightly aided by the spines. It can 

 travel either on the back or stomach ; whatever their posture, they 

 have always a certain number of prickles, which carry them, and 



