296 THE OCEAN WORLD. 



of sixty vessels, having a hundred men on board, had left Madagascar 

 two months previously in the same pursuit. 



Among the Holothuria, one particular genus, Synapta, is distin- 

 guished from others of the family by the absence of the ambulacral 

 feet, and by the fact of its uniting both sexes in one individual. 

 Synapta Duvernaa is represented in PLATE X. M. Quatrefages, who 

 discovered it in the Channel, gives the following description of it in 

 his work, " Les Souvenirs d'un Naturaliste." " Imagine," he says, " a 

 cylinder of rose-coloured crystal, as much as eighteen inches long and 

 more than an inch in diameter, traversed in all its length by five 

 narrow ribbons of white silk, and its head surmounted by a living 

 flower, whose twelve tentacles of purest white fall behind in a graceful 

 curve. In the centre of these tissues, which rival in their delicacy 

 the most refined products of the loom, imagine an intestine of the 

 thinnest gauze gorged from one end to the other with coarse grains of 

 granite, the rugged points and sharp edges of which are perfectly 

 perceptible to the naked eye. 



" But what most struck me at first in this animal was, that it seemed 

 literally to have no other nourishment than the coarse sand by which 

 it was surrounded. And then, when, armed with scalpel and micro- 

 scope, I ascertained something of its organisation, what unheard-of 

 marvels were revealed ! In this body, the walls of which scarcely 

 reach the sixteenth part of an inch in thickness, I could distinguish 

 seven distinct layers of tissue, with a skin, muscles, and membranes. 

 Upon the petaloid tentacles I could trace terminal suckers, which 

 enabled the Synapta to crawl up the 'side of a most highly polished 

 vase. In short, this creature, denuded to all appearance of every 

 means of attack or defence, showed itself to be protected by a species 

 of mosaic, formed of small calcareous shield-like defences, bristling 

 with double hooks, the points of which, dentated like the arrows of 

 the Caribbeans, had taken hold of my hands." 



If one of these Synapta is preseived alive in sea-water for a short 

 time, and subjected to a forced fast, a very strange phenomenon will 

 be observed. The animal, being unable to feed itself, successively 

 detaches various parts of its own body, which it amputates spon- 

 taneously. A great compression or ring is first formed, and then the 

 separation of the condemned part takes place quite suddenly. " It 

 would appear," says M. Quatrefages, " that the animal, feeling that it 

 had not sufficient food to support its whole body, was able successively 

 to abridge its dimensions, by suppressing the parts which it would be 

 most difficult to support, jus* as we should dismiss the most useless 

 mouths from a besieged city." 



