1892-93-] The Shipzvorm. 75 



their sawdust into the Sound, the Teredo would learn to like it, and would 

 prefer ' cut-feed ' to cutting up the piles themselves, and thus some good 

 might he accomplished." 



These borers evidently haunt certain localities, as fish do, 

 without any reason as yet known. But in many instances 

 there may be local causes for their non-appearance, such as 

 swift currents from tides, rough water caused by continuous 

 winds, or an admixture in quantity of fresh with sea water. 

 With such a pest, we are very apt to ask the question, What 

 can be the use for it ? The only redeeming quality that can 

 be set against all the evil it does, is that it attacks floating 

 wreckage as readily as other timber, and, by its weakening 

 action, coupled with the force of waves, breaks up derelicts 

 and floating masses of timber, which would otherwise con- 

 stitute serious and dangerous impediments to navigation. 

 From the lowest to the highest grades of animal life, we find 

 ample provision made for the exigencies of existence, in so 

 far as these demand the use of apparatus giving its possessor 

 some advantage or other in the " struggle for existence," but 

 we wonder what the Teredo has to contend with, or who are 

 his natural enemies — unless it be man — once he has ensconced 

 himself in a long timber pile. 



Specimens illustrating the above Paper. 



1. Teredos in bottle taken from wreck. 



2. Planking of boat bored by Teredo. 



3. Teredo norvegica in tube. 



4. Shells of Teredo. 



5. Shell lining of burrow in a large piece of timber. 



6. Pallets of Teredo. 



7. Pholades from Port Seton. 



8. Shells and accessory valves of Pholades. 



9. Limnoria in tube. 



10. Log bored by Teredo and Limnoria. 



11. Timbers, pine and greenheart, bored by Teredo and Limnoria. 



12. Toredo valves under microscope. 



13. Floating timber bored by Teredo. 



14. Blue shale, &c, bored by Pholas. 



15. Blue whinstone bored by Pholas. 



16. Specimen of greenheart. 



