O'Meara — Bejyort on the Irish Diatojiiacew. 235 



XXXYII. — Eepoet oif THE Ieish Diatomace.^. By the Eev. Etjgeite 

 O'Meara, M. a. Part I. (With Plates 26 to 35.) 



[Eead June 28, 1875.] 



It is no-w just a century, since in 1773, 0. F. Miiller discovered the 

 first known diatomaceous form ; nor was' it till ten years after, the 

 same disting'uished author was ahle to add two new forms to. the list. 

 In the year 1824 Agardh published his " Systema Algarum;" and 

 then the number of species was forty-nine, comprehended under eight 

 genera. But if in this province of Natural Science the progress was 

 slow during the first half century, it has been very rapid in the last, 

 owing not only to the number of eminent labourers in this field of 

 research, but also to the greatly improved means of investigation. 

 The number of species in Europe alone, as computed by Eabenhorst 

 in his index, is about 4000, This may be beyond the mark, but; 

 certainly Pfitzer is far short of it when he fixes the total number of 

 known species at about 1000. It is not necessary to enumerate the 

 many authors to whose useful labours the students of this branch of 

 Science are indebted, but special notice should be made of Kutzing, 

 who explored the whole surface of the globe ; and of Ehrenberg, who, 

 not content with the same ample field of investigation, extended 

 his researches into the bowels of the earth. But no authors, perhaps, 

 have contributed so much to the extent and accuracy of our know- 

 ledge, as those who have restricted their labours to some special 

 families, or to the collection and examination of the forms incidental 

 to some country or district. The treatise on the Diatomacese of the 

 ^Clyde has earned for Gregory an imperishable name. The Austrian 

 forms have been described by Grunow. The Prussian by Schuman. 

 The Danish by Heiberg. Those of Sweden and IS'orway by Cleve, 

 and those of Great Britain by Smith in his admirable Synopsis. 



!N'o country would appear more favourable to the growth of these 

 forms than our own, with its extensive sea-coast indented with 

 numerous bays, its rivers and lakes, and mountain ranges. And yet 

 it is strange that Smith, an Irishman, at least labouring professionally 

 in Ireland, should have done but little in exploring its resources, as 

 appears from the fact that, in the case of 389 forms figured and 

 described by him as British, there are not more than about one 

 hundred for which Irish localities have been assigned. Hence it 

 might be supposed that the climate of Ireland is not favourable to the 

 growth of Diatomaceous forms — an impression which is not justified 

 by the fact, as I hope to prove by the present work. 



Eor many years the intervals of professional engagements had been 

 devoted by me to the collection and study of the Irish Diatomaceag ; 

 and a large amount of material had been gathered and arranged when 



K. I. A. PROC, SER. II., VOL. II., SCIENCE. 2 K 



