40 EFFECT OF TRAWLING ON ANNELIDS. 



injured would survive. On the other hand, many fine examples 

 frequent the rocky borders where no trawl can touch them. 

 The delicate heart-urchins are, for the most part, ruined in the 

 trawl, yet the habitat of many is deeply buried in the sand 

 beyond the reach of 'sole '-rope or iron trawl-heads. Then, 

 again, how many liners, how many mussel-, clam-, and oyster- 

 farmers, would gladly subsidise the trawler to remove the 

 swarms of common cross-fishes, whose multitudes form, for 

 acres, a carpet on the bed of the ocean ! 



Not a few annelids, such as sea-mice, nereids, ' scale-backs,' 

 serpulids, and nemerteans are entangled in the ground-rope 

 and the net of the trawl, or in old shells and other debris from 

 the bottom; but the injury to this group, as formerly mentioned, 

 is not great, for many reach the sea alive amongst the -debris, 

 and regenerate lost parts or discharge their ova into the sur- 

 rounding water, or the larvae swim from under the scales or 

 from the sacs. It is an interesting fact in this connection that 

 certain annelids at the breeding season undergo a change of 

 form, leave the rocks, cavities under stones, or other places of 

 shelter, and swim freely in the water (that is, become pelagic), 

 discharging their reproductive elements when thus en voyage. 

 It is during these pelagic periods that the huge Alitta virens 

 (a worm reaching occasionally about 3 feet, and a valuable bait 

 for fishes) is thrown by storms in great numbers on the sands, 

 even before the function for which nature ordained the pelagic 

 period is performed. In the same way, Mr Thomas Scott, and 

 Mr Duthie, recently found the inshore water at Castlebay, 

 Barra, swarming with the sexual forms of a Nereis. An 

 examination of the stomachs of food-fishes shows that such a 

 provision as the foregoing is duly taken advantage of by them, 

 and it is well, since the annelids are destined to perish after 

 the escape of the reproductive elements. This subject was 

 specially treated of many years ago^, and in the recent Reports 

 of the Fishery Board further investigations have been made by 

 Mr Ramsay Smiths Some annelids, again, are purely pelagic, 



1 Invertebrate Fauna and Fishes of St Andrews, p. 101, et seq., and also 

 Dr Day in Literature, Fisheries Exhib. 1883. 



2 Vide Annual Report of the Fishery Board for Scotland, 1895. 



