Clare Island Survey — Fresh-water Algae. 16-3 



the microscopical examination of the material having occupied considerably 

 more than a thousand hours, the district cannot be said to be exhausted by 

 any means. 



When measurements are given, they apply only to the specimens actually 

 measured ; hundreds of specimens of many species were observed, but 

 comparatively few were measured. 



At first I made lists from the different divisions of Clare Island; but as I 

 found they were increasing in similarity as work proceeded, I thought it best 

 to merge them into one. 



Many other Algae were collected, which, on account of their barren con- 

 dition, or by reason of the few specimens seen, could not be determined with 

 certainty, such as species of Oedogonium, Zygnema, Spirogyra, Mougeotia, &c. 



It is possible that a few brackish-water forms, and even a few marine 

 ones, may occur in the list of fresh-water Diatoms, this being due to the fact 

 that some of the fresh-water lakes and pools are close to the sea and often 

 frequented by gulls, and sprinkled with storm-spray from the . sea during 

 gales ; I have noticed this commingling from the Outer Hebrides and similar 

 places. As far as I know, I have not repeated a name in the list of marine 

 Diatoms which had already occurred in the list of those from fresh water. 



To show how marine and fresh-water species get mixed in such places 

 as tidal rivers, I give a list of ten species out of many others from the mouth 

 of the Bunowen River, Louisburgh, at about the limit of high tide ; the first 

 five are fresh-water forms, the others marine ones : — Geratoneis Arcus, Melosira 

 varians, Sitrirclla ovalis, Gom/phonema const rietum, Syncdra Ac us, Hunt zschia 

 virgata, Rhahdonema adriaticum, Amphora salina, Navicula palpcbralis, and 

 N. digitoradiata. 



As other reports of the series (see Report 10, Phanerogamia) have dealt or 

 will deal with questions of soil, &c, it is only necessary for me to say that the 

 prevalent soil where most of the collections were made is peaty, that the rain- 

 fall is heavy — about 60 inches — and that the climate is mild even in 

 winter. 



I must here express my great indebtedness to Mr. J. Adams, M.A., for the 

 trouble he has taken in kindly adding up the number of species, &c, and 

 analyzing the new records for tabulation. 



Species now for the first time recorded for Ireland are distinguished by 

 an asterisk ; those new to the British Isles by two asterisks ; while species, 

 varieties, and forms new to science are printed in capital letters. 



A2 



