178 The Irish Naturalist. May, 



Polystichum aculeatum in Co. Dublin. 



Oil the 25th March last I started on a walk with the object of making 

 a search for Polystichum aculeatum in the part of the Co. Dublin lying west 

 and south-west of Balbriggan. I had a remembrance of having seen, 

 some 15 or 20 years ago, a number of plants of this fern growing by a 

 road-side somewhere in the district between Balbriggan, Naul, and 

 Skerries; but, although my memory was clear as to the identity of the 

 species, I had only a very general and indefinite recollection of the 

 locality of the place where I had seen it. I had failed in a previous 

 search (in last September), but on this second excursion I was fortunate 

 enough to find the plant. It grows, for a distance of about a quarter of 

 a mile, or more, along both sides of the road south of Walshestown House, 

 and in District I. of the Flora of Co. Dublin. I also found some plants 

 on the road leading to Nevitt from The Five Roads, and I think it 

 is probable that it occurs in other places on the hedge-banks of the fields 

 and roads in the neighbourhood. 



W. O'Brien. 



Mr. O'Brien has kindly sent me a fine living specimen of this fern from 

 the Walshestown locality, and has also shown me the MS. of the above 

 note, which is of great interest, as being the first altogether satisfactory 

 Dublin record for this rather critical species. Its title to a place in the 

 Co. Dublin flora is now established beyond all doubt. 



N. Colgan. 



ZOOLOGY. 



The problems of an Island Fauna. 



As Mr. Moffat in his extremely interesting address on the above subject 

 {Irish Naturalist, April, 1907), alludes to my work on kindred problems in 

 such flattering terms, I may be permitted perhaps to offer a few remarks. 

 In drawing attention to the former occurrence in Ireland of the Lem- 

 mings, which I considered to be of Asiatic origin, and to have entered 

 Europe with the great Siberian invasion, Mr. Moffat justly criticises the 

 arguments advanced by me in respect of the absence of the Eastern fauna 

 from this island. I have rectified this error in a new work on European 

 animals, which is now in the press. The Lemmings in Europe must 

 have come from the North with the Arctic Fox and Hare, and have 

 formed part of the Arctic invasion. They survived the entry of the 

 Eastern group, and their remains are frequently intermingled on the 

 Continent. 



Mr. Moffat asks the pertinent question — Do island faunas tend to de- 

 crease ? With the data available I think we are scarcely justified in 

 assuming such a tendency. As regards Japan, its fauna as a whole is 



