ZOOLOGY 



MARINE ZOOLOGY 



It is quite impossible, in an article of this nature, to treat the invertebrate 

 fauna of the sea fringing the coast of Lancashire in anything like detail. 

 An immense amount of investigation has been carried out during the last 

 tw^enty years, and the fauna and flora of the Irish Sea have now been investi- 

 gated more completely than most other similar areas of the British seas, the 

 Firth of Forth and St. Andrew's Bay in Scotland and the English Channel 

 being excepted. There are now two biological stations in the northern part 

 of the Irish Sea — one at Piel in the Barrow Channel, and the other at Port 

 Erin in the Isle of Man. Four distinct organizations — the Lancashire Sea 

 Fisheries Committee, the Liverpool Biological Society, the Liverpool Marine 

 Biology Committee, and the Southport Society of Natural Science — are now in 

 existence and are still investigating Lancashire waters. The marine zoology 

 of this area has therefore received and is still receiving very considerable 

 attention. 



Physically the Irish Sea is for the most part a shallow water basin. The 

 North Channel which connects it with the Atlantic and the Firth of Clyde 

 is, in places, of considerable depth (over 140 fathoms), and on the south 

 St. George's Channel varies from 40 to about 90 fathoms. To the westward 

 of the Isle of Man there is a deep depression in which depths of 50 to 80 

 fathoms may be found. With these exceptions the greater extent of the Irish 

 Sea area is comparatively shallow. The southern entrance is wide, but the 

 northern inlet is very restricted, and to this cause is due the peculiar conditions 

 of the tides. The tidal wave coming in from the Atlantic impinges obliquely 

 on the south-west coast of Ireland, and there splits up into three main streams. 

 One of these passes up the English Channel and enters the North Sea through 

 the Straits of Dover, but, becoming reflected from this narrow outlet, sets up 

 very peculiar tidal phenomena. Another main stream passes up the Bristol 

 Channel, producing the high tides in the Severn. The remaining stream 

 passes up through St. George's Channel into the Irish Sea. Continuing on, 

 the Atlantic tidal crest passes round the north of Scotland, entering the North 

 Sea, but a part of it also runs down the North Channel, and so enters the 

 Irish Sea from the north. Thus there are two main tidal streams entering 

 the latter basin from different directions, but in consequence of the much 

 wider southern channel, more water enters the Irish Sea from the south than 

 from the north. There is therefore a very evident surface drift of the water 

 .from south to north, helped no doubt by the prevailing west to south winds. 



These two tidal streams meet in a straight line drawn from the north of 

 the Isle of Man across to Morecambe Bay, and from the Isle of Man to the 

 Irish coast. Between the Irish and Manx coasts there is a large area where 

 tidal streams practically do not exist, and where the water simply rises and 

 falls. All along the east Irish coast the velocity of the stream is small, but 



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