312 THE ACCURACY OF THE OBSERVATIONS [APP. IV 



the eggs and larvae of Luidia, a bottom-living sea urchin, were 

 distributed through a very large area of the North Sea, although 

 Luidia is a deep sea animal and is found only in two or three parts of 

 the North Sea (see Hensen's Taf. XVII.). Of course the animal may 

 have a much wider distribution than we suspect, but we have no right 

 to assume this merely to discount the bearing of the fact of its wide 

 distribution on Hensen's general statement. The bottom fauna of the 

 North Sea is in fact pretty well known and if Luidia were generally 

 distributed over the entire area it would have been more frequently 

 found. 



Again the sand-eel and the flounder are both shallow water fishes, 

 that is, predominantly so. If these fishes spawned in the shallow 

 water off" the coast, and if there were no means whereby their eggs 

 became widely distributed, then we should expect to find them in a 

 comparatively restricted area near the land. But the fishes in 

 question are shallow water spawners, and yet we find their eggs over 

 the greater part of the North Sea, a fact which seems to me to justify 

 us in concluding that there are unlikely to be any very considerable 

 segregations of pelagic eggs in the sea, and therefore that the method 

 of the Nordsee Expedition was a valid one. Nevertheless we must 

 not forget that the limits of error in the results are somewhat wide ; 

 and that in the application of these results this limit must have a 

 certain relation to the conclusions that have to be made. 



