462 Mr. J. Ralfs on the Biitish species of Gomphonema. 



Ehrenberg appears to have confounded this plant with Gom- 

 phonema geminatum, Ag., which species, as well as the Gomph. 

 pohliaeforme of Kutzing, he appends as synonyms to his Gomph. 

 truncatum^. If he had seen the true Gomph. geminatum he could 

 not have fallen into this mistake, for besides the immense differ- 

 ence between these plants in size and habit, their frustules possess 

 sufficient marks of distinction. In Gomph. geminatum the front 

 view is very narrow, sometimes nearly linear ; in this species they 

 are distinctly cuneate, and notwithstanding their much smaller 

 size, have two evident notches at the upper end, which are want- 

 ing in Gomph. geminatum. The lateral surfaces too are more at- 

 tenuated at the base, and they are about as broad as the front, 

 whereas in Gomph. geminatum they are much broader. 



Plate XVIIT. %. 4. Gomphonema pohliaforme. 



3. G. minutun, Ag. Minute ; frustules with a terminal crest ; la- 

 teral surfaces striated, constricted below the apex ; laterally viewed, 

 the end of the crest appears like a terminal point. Ag. Consp. 

 Diatom, p. 34; Grev. in Hook. Br. Fl. vol. ii. p. 410. Gomph. 

 acuminatum. Eh. Die Infus. p. 217. 1. 18. f. 4 ; Pritch. Infus. p. 228. 

 On aquatic plants in ponds and ditches. Sussex, Mr. Jenner; 



Herts, Mr. Hassall ; Barmouth, Rev. T. Salwey ; Trengwainton 



ponds near Penzance, and pond on Towednack Moor near St. Ives, 



Dolgelley. 



This species, which forms a brownish mucous fringe on the 



• It is greatly to be regretted that Ehrenberg has in so many instances 

 disregarded ths names previously affixed by Agardh and Kutzing. To alter 

 a name once- bestowed is not only discourteous to the first describer, but 

 creates confusion and tends to encumber the science with synonyms ; for if 

 it be allowable for one v/riter to alter a name because he fancies that a new 

 one is more appropriate, succeeding writers have an equal right to alter his 

 names, and in the absence of a recognised rule, some naturalists may prefer 

 one name and some another. 



There is an e:icellent paper on Nomenclature in the * Annals of Natural 

 History/ vol. xi. p. 259, which is deserving of consideration, not only be- 

 ' ause it wag written at the request of the British Association, but also from 

 the celebrity of it& authors. Although it is more particularly addressed to 

 zoologists, yet great part of it may be equally useful to botanists, and some 

 of the remarks are so appropriate to the present subject that 1 cannot forbear 

 quoting them. 



" The names originally given by the founder of a group, or the describer 

 of a species, should be permanently retained to the exclusion of all subse- 

 quent synonyms. 



" No one person can subsequently claim an authority equal to that pos- 

 sessed by the person who is the first to define a new genus or describe a new 

 species, and hence it is that the name originally given, even though it may 

 be inferior in point of elegance or expressiveness to those subsequently pro- 

 posed, ought as a general principle to be permanently retained. To this 

 consideration we ought to add the injustice of erasing the name originally 

 selected by the person to whose labours we owe our first knowledge of the 

 subject." 



