112 MR. R. GURNEY ON LEANDER LONGIROSTRIS 



down, but it is found in abundance, at all events in the breeding- 

 season, even when the water is entirely salt. On the other hand, 

 the numbers are generally found to increase towards the upper 

 end of the estuary. It is never taken at sea by the shrimpers, 

 though it is said to be caught occasionally just at the mouth of 

 Yarmouth Harbour. Mr. Patterson has sent me specimens taken 

 at St. Olaves on the Waveney, and probably its distribution is 

 continuous from Yarmouth to Oulton Broad via the Waveney. 

 No doubt it also occurs in the Yare, at least as far as Reedham, 

 but I have not been able to search for it there. In the Bure it is 

 common, probably at all states of the tide, as far up as Acle, 

 14 miles from the sea, and I have even taken it in Heigham 

 Sounds, 22 miles from the sea. It is well known to the eel- 

 catchers, and numbers are taken in the eel-nets at certain times. 

 At South "Walsham eel-set they are usually found in the net after 

 there have been high salt tides in the river and the salt water is 

 beginning to run down again. At such times they are also 

 commonly taken in an eel-set near Hickling Broad. 



To judge from its distribution in Norfolk, L. longirostris is 

 essentially a river prawn capable of existing either in salt or in 

 fresh water, but preferring that part of the river in which the 

 water is generally brackish. Their indifference to salinity is such 

 that they may be repeatedly transferred dii-ectly from fresh water 

 to salt and vice versa without any apparent ill-effects, and I have 

 at this moment a number which, taken originally in salt water, 

 have been living for months in pure fresh water. One of these, 

 after hatching her young in salt water in June 1921, was trans- 

 ferred to a fresh- water aquarium in which she moulted 10 days 

 later, and is still (November 1922) flourishing. This indifference 

 to salinity can be equalled by very few animals and surpassed by 



Breeding. 



The fact that, in order to catch L. longirostris with certainty 

 and in any numbers, it is necessary to use a trawl either in the 

 lower reaches of the rivers or in Breydon Water, has rather 

 restricted my opportunities for observation, and I have not been 

 able to get representative collections throughout the year. It 

 is, however, certain that breeding begins at the end of May or 

 beginning of June, as it does in L. squilla, and that two broods 

 are hatched in the season. A number of specimens taken far up 

 the River Bure on May 16, had ripening ovaries, but no eggs 

 had been laid, but on June 15, 1922, out of 98 females taken 

 in Breydon Water, 48 bore eggs in various stages, 42 had hatched 

 but had not moulted, while 8 had hatched and moulted, and were 

 ready to lay another lot of eggs. All, except one with freshly- 

 laid eggs, had the ovary full. As development probably takes at 

 least a month, and the moult following hatching occurs usually 

 4 or 5 days later, the first eggs must have been laid this year 

 about May 10. No doubt the larger two -year -old prawns 

 spawn about the middle of May, and are followed towards the 



