The Fresh-water Sp07iges of Irela?id. 125 



The following therefore are the Fresh-water Sponges so far 

 found in Ireland : — 



1. Euspongrilla acustris, Autt. Camlough River, Co. Armagh; 



Dry drain, Killakeen. Probably common throughout the 

 country. 



2. Ephydatia fluviatilis, Autt. River Barrow ; Raheny ponds, Co. 



Dublin. Probably common throughout the country. 



3. Ephydatia lYIuIIeri, Lieberktihn. McHugo Island, Lough Rea, 



Galway. 150 feet above sea level. 



4. } Ephydatia crater if orm is, Potts. Park Lough, Hungry Hill. 



300 feet above sea level. 



5. Hetcrotneycnia Ryder i, Potts. Lough Doon, near Dingle. 



1,000 feet above sea level. 



6. Tubella pennsylvanica, Potts. Columbkille Lough, Bally- 



shannon. 100 feet above sea level. 



In this list we notice the important fact that the eastern 

 part of Ireland possesses only common European forms (Nos. 

 I and 2), but that the American species (Nos. 4, 5 and 6) are 

 found only along the west coast, and there, so far, only one 

 European species (No. 3) has been obtained. 



How can we account for the occurrence of those American 

 Spongillidae in Ireland ? Wallace (12, pp. 364 and 365) men- 

 tions several flowering plants, viz. : — Spiranthes Romanzoviana, 

 Sisyrinchium a7igustifolium and EriocatUon septangular c, which 

 are American, and yet have been found in the west of Ireland, 

 and he thinks that these American plants, together with a few 

 arctic and alpine plants, ma}^ be the remnants of a vegetation 

 once spread over the whole north temperate zone. Similarly, 

 we might explain the occurrence of American Spongillidae in 

 Ireland. But, at least in the case of the Spongillidse, it seems 

 to me quite as likely that such forms migrated from North 

 America to Ireland. The formation of gemmules gives to the 

 Spongillidae such chances of dispersal, as only few animals 

 enjoy, comparable in fact to the dispersal of plants by means 

 of seeds. In the February number of this journal Mr. G. 

 H. Carpenter recorded from the Mitchelstown Caves, Co. 

 Tipperary, a collembolan, Sinella cavernicola, almost, and a 

 spider, Porrhommamyops, quite indistinguishable from species 

 inhabiting the Kentucky and other North American caves. 

 But insects too are very easily dispersed. Only in case of the 

 discovery in Ireland of American animals whose presence 

 could not be explained by dispersal in recent times, should 



