40 NATURE'S TEACHINGS. 



may be seen an anchor so exactly similar in form, that the 

 outline of the one would almost answer for that of the other. 

 This object is a much-magnified representation of a spicule 

 which is found on the skin of the Synapta, one of the so-called 

 Sea-slugs, which are so extensively sold under the name of 

 Beche de Mer. It forms one of the curious group called the 

 Holothuridae. 



Each of these anchors is affixed to a sort of open- worked 

 shield, as shown above, and on the left hand ; and it is a curious 

 fact that in the various species of Synapta the anchor is 

 rather different in form, and the shield very different in pattern. 

 They are lovely objects, and I recommend any of my readers 

 who possess a microscope to procure one. They need a power 

 of at least 150 diameters to show their full beauties. 



An ordinary Grapnel is here shown, and in the corresponding 

 position on the opposite side is an almost exactly similar object, 

 except that it is double, having the grapnel at both ends of the 

 stem. This is a spicule of a species of sponge, and is one of the 

 vast numbers of which the sponge principally consists. 



LERNENTOMA. ECHINOCOCCUS. SI'ONGE-SPICULK. 



Next to the sponge-spicule is a still more perfect example 

 of a natural Grapnel. This is the head of an internal parasite 

 called Echinococcus, which holds itself in its position by means 

 of the circle of hooks with which the head is surrounded. 

 These hooks are easily detached, and have a curious resemblance 

 to the claw of the lion or tiger. 



On the left-hand side is a representation of a parasitic crus- 

 tacean animal called Lernentoma, which adheres to various 

 fishes, and is mostly found upon the sprat, clinging to the gills 

 by means of its grapnel- shaped head. 



On the right hand of the accompanying illustration is an ice- 

 anchor, copied from one of those which were taken out in the 



