64 The Shipworm. [Sess. 



(3) Some few hybrids lean to one parent. (4) Geum inter- 

 medium, an undoubted hybrid between Geum rivale and 

 Geum urbanum, is in every respect a better plant than 

 either parent. 



Dr Macfarlane's observations seem to me in accordance 

 with the views held by Strassburger of Bonn, that the great 

 advantage of crossing is that any defect or disease which may 

 have sprung up in one parent is likely to be got rid of by 

 crossing, because it is unlikely that the very same defect will 

 occur in the other parent. At the same time, it is apparently 

 the vegetative organs which are most improved by crossing. 

 The reproductive organs may not be improved, and in some 

 cases they may even be impaired. 



VII — THE SHIP WORM. 



By Mr WILLIAM COATS. 



(Read Feb. 24, 1893.) 



One of the most dreaded of marine enemies which the ingenuity 

 of man has ever been exercised to encounter, and with such 

 signal lack of success, is undoubtedly the Teredo or Shipworm, 

 — the " calamitas navium " or " terror of ships," as Linnaeus 

 termed it ; and for the loss of many a stately ship it must be 

 able to account. This animal is notorious for the deadly havoc 

 it makes of the planks and timbers of ships, the piles of piers, 

 clocks, and marine woodwork of every description and in 

 almost any situation and climate. An entrance once secured, 

 it honeycombs timber to such an extent as to deprive it of all 

 strength, leaving it, however, with an outward semblance of 

 stability. With such an enemy, working, as it were, in the 

 dark, it is only when disaster or accident happens that the 

 real extent of the mischief is discernible, and its ravages 

 within a decade must represent vast sums in our national 

 expenditure. It has been known, by its effects at least, for 

 centuries. In the following translation we find Ovid — 



