THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL 



YoL. IT. 



New York, December, 1881. 



No. 12. 



Fineness of Striation as a Speci- 

 fic Character of Diatoms. 



BY PROF. H. L. SMITH, HON. F. R. M. S. 



The October number of the Jour- 

 nal of the Royal Microscopical Society 

 contains a translation of Count Cas- 

 tracane's paper, " On the Value to be 

 Attributed, in the Determination of 

 Species, to the Number of the Striae 

 of the Diatomaccce," in which he 

 arrives at the following conclusion : 

 " The striae and their fineness are a 

 quality of specific importance.''' In a few 

 words appended to this translation, 

 Mr. Kitton, the well-known English 

 diatomist, criticises Count Castra- 

 cane's conclusions, and indicates the 

 mistakes of the Count himself in 

 his attempt to make these measure- 

 ments, which he deems of specific 

 importance. The conclusion of the 

 Count, however, will be heartily wel- 

 comed by " species mongers," inas- 

 much as one need have little fear in 

 being able to sustain the claim to n. 

 sp. if allowed to fall back on stria- 

 tion as the test, for, who shall decide ? 

 Not every one has at command the 

 elaborate apparatus used by Count 

 Castracane for determining the num- 

 ber of Stri«. Photographs of each 

 diatom, — projections on an enlarged 

 scale, etc., — seem to be considered 

 by him as the only trustworthy me- 

 thod ; a method of such exactness 

 *hat it " enables him to disagree with 

 xuicroscopists of incontestable au- 

 thority." For Count Castracane per- 

 sonally, and as a correspondent and a 

 thoroughly conscientious, hard-work- 

 ing diatom-student, I have the 

 highest respect, but I am sorry that 

 he has felt himself obhged to adopt 



so pernicious a view, as it seems to 

 me. The diatomaceae belong to the 

 vegetable world and the principles 

 governing their classification and 

 arrangement, need not be very 

 different from those accepted for 

 other portions of the vegetable king- 

 dom. It would seem that with as 

 much propriety, one might consider 

 the number of granules on a Stau- 

 rastru?n or striae on the frond of a 

 Clostei'ium, of specific importance ; 

 or the number of fibres in a given 

 space of a specimen of pine or oak, 

 of value in determination of species. 

 I venture the assertion, that if one 

 were to show to the distinguished mi- 

 croscopist who has advocated this 

 view of the importance of fineness of 

 striation, a slide of diatoms, and re- 

 quest him to say what they were, he 

 would name them all, correctly too, 

 and never once resort to measurement 

 of striation to do so. Now, if this 

 can be done, and it is done every day 

 by experienced microscopists, what 

 is the necessity of bringing in an ele- 

 ment which most students of the Dia- 

 tomacese consider very variable and 

 exceedingly difficult to determine ? 

 I would not have it understood, by 

 what I have said, that I consider 

 striation as of no importance ; in 

 conjunction with other things, it has 

 a certain value, but at best only se- 

 condary. 



I do not suppose that Count Cas- 

 tracane would, for a moment, assert 

 that Stauroneis Phoe.nice7iteron, e. g. 

 has the same number of striae in .001 

 of an inch as Stauroneis gracilis^ and 

 yet I have frequently found the lat- 

 ter conjugating and the sporangial 

 frustule is S. Phanicenteron. The spor- 



