236 Proceedings of the Royal Irish Academy. 
I was favoured with the request of the Royal Irish Academy to 
prepare a list of the forms to be met with in this country—a request 
with which I unhesitatingly complicd. Had I been content with 
furnishing an inventory of the forms I had found, the task I had 
undertaken might have been speedily performed; but my anxiety was 
to render the work as complete and as useful to my fellow-students as 
I could, and as worthy of the reputation of the Royal Irish Academy 
as it was possible for me to make it. With this view I determined to 
explore new localities, and to search more carefully, districts I had 
previously examined. JI was anxious also to avail myself of the 
labours of the most distinguished authors on the subject, and was 
therefore obliged to acquire a knowledge of languages with which I 
was previously unacquainted. 
For all this, time was required, and I refer to the subject for the 
purpose of showing that the long period that has elapsed since the task 
was undertaken has been busily, and I hope not fruitlessly, occupied. 
No authentically named specimens were available; and this proved to 
me a source of much additional labour and delay. Those who are 
practically acquainted with the Diatomacez are aware how difficult it 
is sometimes under the most favourable circumstances to identify a 
form. The difficulty is enhanced in cases in which the original 
form, observed under the disadvantage of inferior instruments, has 
been inadequately described ; and when a mistake has been made 
in the figure or the description, the only satisfactory means of identifi- 
cation is the inspection of the specimen. Hence some idea may be 
formed of the difficulty and delay arising from the circumstance 
of there being no authentic specimens preserved in any of the- 
Collections or Herbaria of Dublin. Many are the friends who have 
kindly assisted me in the prosecution of this work, but special acknow- 
ledgments on my part are due to Professor E. Perceval Wright, M.D., 
not only for the loan of collections but also of books and objectives, to 
Rey. Maxwell H. Close, and A. G. More, Esq., whose collections have 
added numerous forms to my list, as well as new localities for many 
others; and also to Dr. David Moore, whose many and valuable 
collections were kindly placed at my disposal. 
The name of Bacillariacesee was employed to designate this group of 
organisms at a time when Little of their structure and habits, except 
their outward form, was known; and Pfitzer maintains that this desig- 
nation should be retained because of its priority: but I have adopted 
the more modern name of Diatomacez, not only because it is more 
pronounceable, but specially because it is more characteristic and more 
generally known. 
The question, what is the proper position of the Diatomacez in the 
classification of organized beings, has been variously answered. The 
first known species were by their discoverers included amongst the 
Confervacee ; the extraordinary movements, however, of Bacillaria 
paxillifer, noticed by Miller, induced that author to identify it with 
the genus Vibrio; and the position assigned to this form, as well as 
