240 FUNCTIONS AND INSTINCTS. 



internal bone or gristle, but upon which they 

 can turn as upon a pivot, and so in due time 

 effect their destined purpose. 



I shall now proceed to furnish some examples 

 of the manner in which this is effected : and give 

 an account of some of each of these tribes, 

 beginning with those, and they are numerous, 

 that make the burrows in the sand to a consider- 

 able depth, so that it presents a less solid mass 

 to the action of the waves. 



I shall first call the reader's attention to the 

 proceeding of one usually denominated the razor- 

 shell, from the supposed resemblance of some of 

 the species to that instrument ; in substance and 

 colour they are often like the human nail, and as 

 they, as well as the stone-borers, are stated to 

 emit a phosphoric light, and also are eaten, it 

 seems to me most probable that they are the 

 animals and not the pholad as is usually sup- 

 posed, which the Roman naturalist describes 

 under the name Dactyle* These animals burrow 

 in the sand, sometimes to the depth of two or 

 three feet, and never quit the burrow unless by 

 force. Poli says the collectors of them are 

 accustomed to pour oil upon the water, which 

 renders it quite transparent so that they can dis- 

 cern the razor-fish in its burrow by its tubes 

 which are exerted. So powerful are its strug- 

 gles, that, though they wind linen about their 



1 See Appendix, note 23. 



