A HISTORY OF NORFOLK 



2^ inches in length, a size never attained in the river, nor, I believe, in 

 the Wash itself. 



' The position of the pits is about three-quarters of a mile from the 

 Roman banks on the land side, and a mile and a half from the river Nene, 

 up which the same species comes with the tide. 



' There are many pits in this district in which the water rising from 

 the silt is brackish, but I have never met with another case in which 

 marine organisms were found living, though nearly every pit within an 

 area of i,ooo square miles was examined. In some places a communica- 

 tion is kept up with the sea by beds of quick-silt, and wells become 

 distinctly brackish during high spring-tides. In the present instance 

 such does not seem to be the case, and one is driven to the conclusion 

 that the prawns must have been introduced accidentally, or that the ova 

 were embedded in the silt itself. 



' It is highly improbable that the prawns were introduced wilfully 

 for the mystification of naturalists, for the latter are rarer than prawns 

 about here, and the time of the appearance of the prawns just after the 

 spring was tapped, and the fact of them all being very small at first are 

 in favour of a natural mode of introduction. Neither is it probable that 

 the ova were introduced by sea-birds in one of their very rare visits to 

 this pit, for the ova are carried by the females until they hatch, and could 

 not become attached to the bird, neither could they have survived the 

 process of digestion as some seeds do. Besides, considering the great 

 number of open pits hereabouts which have been unused for years, and 

 so afford much better protection for sea-birds, the introduction of 

 prawns ought to have been more general on such a supposition. True, 

 most of the pits contain fresh, or only slightly brackish water, but prawns 

 seem to live almost as well in fresh as in salt water, and I have frequently 

 noticed them miles above locks on tidal streams, where the water is not 

 even approximately brackish. The prawns in question were kept for 

 weeks in fresh water, and they were then killed by accident. Neverthe- 

 less, in no other pit have they been found, though they would hardly 

 escape notice, since these spots afford valuable fishing resorts. 



' The balance of evidence is decidedly in favour of the burial of the 

 ova in the silt, which is so quick as to be dangerous to stand upon, and 

 would afford plenty of water for their preservation. The only difficulty 

 attaching to this supposition is the length of time during which the ova 

 must have lain dormant. The Roman banks are about 1,700 years old, 

 and at least 3,000 years must have elapsed since the area of the pits at 

 the depth in question was covered with sea water. Yet I see no other 

 explanation, and am strongly inclined to believe such to have been the 

 case.' 



On this passage several comments may be made. The author 



seems to speak of prawns as if they all had the same habits and were 



all of one species. That he is really speaking of Palamonetes varians 



has to be inferred from the statement that specimens lived for weeks 



in fresh water. On the other hand, a size of 2| inches, though often 



190 



