PRESIDENTIAL ADDRESS. 



29 



Adams thestations and the habits have materially changed." 

 Where Adams had gathered 4,500 specimens of Oliva 

 volutella, Presbrey got three. Adams took 1,500 Nassa 

 panamensis and 330 N. luteostoma near the old sea wall 

 where there are none now. Where Adams took 3,000 

 specimens of Columbella representing 29 species, there 

 Presbrey merely saw a few individuals of seven species. 

 It may be that this depreciation was partly caused by the 

 opening of the Panama Canal, but the changes involve 

 some gain as well as heavy loss. For in other cases the 

 species noted as rare by the first investigator had become 

 abundant in the time of his successor. Strombus galea, of 

 which Adams only saw a few fragments, is now plentiful, 

 and Purpura is more common than it used to be. Both 

 Pecten and Pectuneulus were rare in 1850 and common in 

 1913. 



Striking changes which occurred in the marine fauna of 

 Plymouth between 1893 and 1895 are noted by Mr. E. T. 

 Browne. 1 



Changes by Epidemics and Accidents. 



The desolating sweep of a bush fire is unknown in the 



marine world, but the sea is not exempt from destructive 



visitations. Our fauna though safe from being scalded by 



hot lava, or planed away by floating ice, has its own plagues. 



Sudden and widespread mortality occurred among the 

 sedentary intertidal organisms of Port Jackson in 1866 and 

 again in March 1891. Oysters and mussels were com- 

 pletely exterminated over wide areas, the stench from the 

 mussel beds at Watson's Bay was described as unbearable. 

 At Little Sirius Cove all the limpets and periwinkles were 

 found to be lying about with the animals decaying in the 

 shells. Such forms as live under stones, the zoophytes, 



1 Browne, Journ. Marine Biol. Assoc, iv, 1896, p. 168. 



