KITTON, ON DIATOMACEiE. 141 



Philosopliical Journal/ July, 1859) much too closely to 

 warrant its separation from that species. 



The Rev. E. O'Meara remarks, " that our department of 

 science has heen embarrassed by an excessive nomenclature 

 must be obvious to every experienced observer. The evil is 

 traceable in some considerable degree that the descriptions 

 of species are not as comprehensive as might be." Surely 

 the reason why they are not so, obviously arises from the 

 circumstance of so many new genera and species being 

 constituted from unique or rare specimens, and until the 

 system of making new species of scarce forms is abolished, 

 this evil will continue. Before a species can be correctly 

 described, it is necessary to see it in a living condition, and, 

 if possible, its sporangial form. A botanist, before he 

 published a new species, would require to see more than a 

 few leaves. In conclusion, I venture to quote two or three 

 authorities whose opinions are of infinitely greater weight 

 than mine. 



Dr. Berkeley (in the preface to his ' Cryptogamic Botany ') 

 says : " So long as essential characters are neglected, *and 

 fleeting external characters put in their place, difficulty 

 must needs exist, and the student will never be certain that 

 he has come to a correct decision till he has seen an au- 

 thentic specimen, or compared his own with that of other 

 botanists, as manifested in extensive herbariums. A state of 

 uncertainty is always one of more or less pain, and the 

 temptation to a solution of the difficulty by the supposition 

 that he has made a new discovery present such attractions as 

 to appear insurmountable. Nor will he find it possible, 

 without that mental discipline which arises from a patient 

 study of every detail of structure, and of the various shapes 

 which organs may assume under different circumstances. 

 The great point in all cases is never to describe from single 

 or imperfect specimens, where there is some form evidently 

 very closely allied. A proposer of bad^ ill-defined species is 

 no promoter of science.'^ Another acute observer (Dr. G. 

 A. W. Arnott), whose knoM'ledge of diatoms is perhaps 

 superior to that of any other observer of those forms, says, 

 in his paper on " Rhabdonema " (vol. vi, p. 87, of this 

 Journal), " That it is better not to publish a new species, or 

 give it a name, than to do so from scanty or imperfect 

 material, which leaves both genus and species doubtful. 

 Even now I have some hesitation in writing on the subject, 

 as my views are diametrically opposed to those who consider 

 it necessary to give names to forms which to the eye appear 

 distinct, butwhich have not structural differences sufficient for 



