STARFISHES SEA URCHINS 165 



tube, that extended into it. But no inconvenience attaches itself 

 to this loss, for the starfish has the power of reproducing even 

 its lost viscera, as well as any of the five rays of the body that 

 may be broken off. 



We must briefly refer to one other feature of the common star, 

 viz. the possession of small prehensile organs around the mouth. 

 These are little spines, the extremities of which are movable, and 

 take the form of little pincers by means of which the animal can 

 hold its prey. 



"When it is desired to preserve starfishes for future study, 

 immersion in diluted spirit or a solution of formaldehyde will answer 

 all purposes, the soft parts being thus preserved as well as the 

 harder structures ; but it is usual to preserve them in a dry state 

 when they are required merely for purposes of identification, as 

 is usually the case with the specimens in an ordinary museum 

 collection. In the latter case it is advisable to put the starfishes 

 in strong spirit for a few days, changing the spirit if several speci- 

 mens are put together, and then drying them as quickly as possible 

 in the open air. 



We have now to consider the Sea Urchins or Sea Eggs, which 

 are readily known by the hedgehog-like covering of hard spines. 

 Externally they appear as globular or heart-shaped bodies, the 

 surface entirely hidden by spines except, perhaps, the mouth on 

 the under side, which is provided 

 with an apparatus for mastica- 

 tion. If alive, and in the water, 

 one may notice that the animal 

 creeps along the bottom, mouth 

 downwards, moving itself either 

 by means of its moveable spines, 

 or by soft tube-feet resembling 

 those of starfishes, that are pro- 

 truded between the spines, or by 

 both combined ; and the move- 

 ments of its masticating organ may 

 be seen by observing the animal J^G. 108. SECTION OF THE 

 through the side or bottom of a SPINE OF A SEA UKCHIN 



glass vessel of sea water. The last- 

 named organ is surrounded by an area of soft skin, and is not 

 present in all species. 



A closer examination of the common globular urchin will show 



