44 EFFECT OF TRAWLING ON SHELL-FISHES. 



contained embryos in a thin capsule nearly an inch in diameter, 

 were in perfect condition, and are now in the University Museum. 

 These mussels occur in deep water, and often form large masses 

 bound together by the threads of the byssus or 'beard,' and 

 are quite as frequently drawn up by the liners on their hooks 

 on their particular ground. Moreover, some of the liners for 

 years used to bring quantities close inshore and deposit them 

 off the rocks, thinking to create a bed of horse-mussels, but all 

 disappeared. Not a trace remains of the many tons of horse- 

 mussels thus transplanted, except an occasional and solitary 

 small example in a chink of the rocks, perhaps an inshore and 

 last surviving descendant of the transplanted shell-fishes. The 

 living whelks were generally entire, those (Fusus) having the 

 rare anemone {Hormathia the ' necklet ') adhering externally, 

 being in perfect condition, just as the much more delicate dead 

 Natica, overgrown with sponge, and tenanted by a hermit crab, 

 often came up uninjured. Masses of the spawn both of the 

 great whelk and Fusus are frequently brought up by the trawl, 

 but much of these is uninjured on again reaching the water. 

 Even on great stretches of sand, in which many shell-fishes 

 abound, comparatively few bivalves are interfered with, since 

 they are buried more or less under the surface, and afford little 

 hold to the ground-rope. The molluscan fauna of muddy 

 ground is also inconspicuous in regard to injury, the smaller 

 forms, which are sometimes numerous, escaping entirely. A 

 single severe storm dislodges those on sandy ground more 

 surely and extensively than years of continual trawling. The 

 spawn of the whelks, and that of the nudibranchs and cuttle- 

 fishes, is more likely to suffer, yet only to a limited extent, 

 since all is again consigned to the water; and even a some- 

 what lengthened exposure on deck is not fatal, if a little 

 moisture be present, since many can be hatched after the 

 arrival of the ship in port. In these remarks trawling over a 

 mussel-bed, a clam-bed, or over an oyster-bed, is not considered, 

 since it is strictly and rightly prohibited. On the whole, then, 

 the shell-fishes do not suffer conspicuous injury by the use of 

 the ordinary trawl, a fact sufficiently plain at St Andrews, 

 where the larger mollusks were eagerly sought for bait by the 



