40 



HARDWICKE'S SCIENCE- G OSSIP. 



that my want of success is due either to my ignorance 

 or to the cHmate. My method of using the varnish 

 is this : placing the cover on the object, I take the 

 varnish from the bottle with a fine pointed glass tube, 

 and, ajjplying it to the edge of the cover, capillary 

 attraction "runs it in" around the object. The 

 varnish does not set. I thought that by putting a 

 light ring of gold size round some of my dammar 

 objects I should fix the cover, and thus prevent it 

 from slipping about, but in twenty-four hours the 

 ■cement had run-in in several places all round the 

 cover. Again — and this occurs, though to a less 

 ■extent, with chloro-balsam — vacant, bubble-like spaces 

 break out all round the edge of the cover, as if the 

 varnish had dried out, and the introduction of addi- 

 ■lional varnish does not mend matters. How are these 

 failures to be explained ? I may add in conclusion, 

 that my own experience leads me to say neither 

 chloro-balsam nor dammar varnish give such good 

 results out here as balsam used by itself in the way 

 pointed out above, viz. with the air-pump. I have 

 mounted many objects in cement cells with glycerine, 

 either pure or diluted, using Shadbolt's turn-table 

 '.\ith complete success. It must be remembered I 

 write in India.— IV. J. S., Calcutta. 



Fineness of Striation as a specific Cha- 

 racter OF Diatoms. — Under this title Professor 

 H, L. Smith, Hon. F.R.M.S., has reviewed (see the 

 " Amer. Month. Mic. Jour." No. 12, vol. ii., which, by 

 the way, with the ' 'Amer. Jour, of Microscopy " should 

 be in the hands of all those interested in microscopical 

 studies) the translation of Count Castracane's paper 

 in the October number of the " Journal of the Royal 

 Microscopical Society : " "On the value to be attri- 

 buted in the Determination of Species to the number 

 of Strirc of the Diatomacere," to which are appended 

 some criticisms of my own. Count Castracane arrives 

 at the conclusion that " the strice and their fineness are 

 qualities of specific importance. As Professor Smith's 

 views are in perfect accordance with my own, I pro- 

 pose to give a resume of his paper." The conclusion 

 of the Count, however, will be heartily welcomed by 

 species-mongers, inasmuch as one need have little fear 

 in being able to sustain the claim to ;/. sp. if allowed 

 to fall back upon striation as the test, for who shall 

 decide ? Not every one has at command the elaborate 

 apparatus used by Count Castracane for determining 

 the number of stria;. Photographs of each diatom- 

 projection on an enlarged scale, &c., seem to be 

 considered by him as the only trustworthy method— a 

 method of such exactness that "it enables him to 

 disagree with microscopists of incontestable author- 

 ity." The Diatomacea.' belong to the vegetable king- 

 dom and [the principle governing their classification 

 need not be very different from those accepted for 

 other portions of the vegetable kingdom. I do not 

 suppjse that Count Castracane would for a moment 

 assert that Slauromis pucniceiiicron, e.g., has the 



same number of striae in •001 of an inch as S. gracilis, 

 and yet I have frequently found the latter conjugating, 

 and the sporangial frustule \% S. phccnicenteroii. There 

 are a great many diatoms of the Navicula firiiia 

 [not J>i/tiia as enoneously printed, F. K.) group, which 

 really pass into each other so gradually that even 

 by the help of striation it is difficult to distinguish 

 them; iV. ajjiiiis produces by conjugation true N. Jinn a, 

 and I have even observed the large frustules of the 

 latter again producing monsters by conjugation far 

 more coarsely marked than the parent frustules. Shall 

 w-e consider the sporangial form as one species and 

 the parent form another ? . . . I am quite prepared to 

 admit that a preparation of the so-called Frustitlia 

 Saxonica, for example, will not show any appreciable 

 difference in the striation of the frustules ; but I should 

 be quite unwilling to admit that this diatom could not 

 be obtained from another locality considerably more 

 finely or more coarsely marked. Indeed Count Cas- 

 tracane himself admits a difference, though he says it 

 has never exceeded \, which, as Mr. Kitton shows, 

 gives a range in N. crassiiicnns, if he understands 

 aright, if 27 to 35 in '001 of an inch! . . . Any one 

 looking over Mr. Habershaw's " Catalogue of the 

 Diatomacere," will realise what a frightful increase of 

 species was made by Ehrenberg and the earlier ob- 

 servers from considering the number of rays in achno- 

 cyclus as of specific value. Equally pernicious is the 

 custom too largely indulged in by many observers, 

 who, looking from the standpoint which Count Cas- 

 tracane appears to advocate, find at stated intervals 

 new species founded upon little else than finer or 

 coarser striation, or perhaps somewhat different out- 

 line. It is no doubt quite a comfortable way of 

 working and keeping one's name before the public, 

 when one finds what is supposed to be a new diatom ; 

 if only knowing enough to distinguish the genus, one 

 measures more or less correctly the length, breadth or 

 diameter, and the number of striae in '001 of an inch, 

 giving sometimes a representation which, if it be one 

 of the smaller NaviciiUc, may too often represent many 

 other forms, and finally to coin some unpronounceable 

 word, or immortalise some friend and send forth the 

 bantling, since nobody can venture to question its 

 legitimacy; for does it not differ somewhat from every 

 form hitherto figured or described in outline? and 

 has it not a few stria; more or less in the '001 of an 

 inch? I shall be very sorry i, in what I have said, I 

 am considered as censuring men who are unquestion- 

 ably hard-working and conscientious students of these 

 interesting little organisms. I am only regretting that, 

 instead of labouring to reduce the genera and species 

 of the Diatomacea; and seeking for a broader and 

 firmer principle to guide in their study and' classifica- 

 tion, so many worthy persons are contented to accept 

 trivial distinctions as of generic and specific value, and 

 that they are so encumbering the subject that some 

 day it will be crushed by ts own dead weight, giving 

 place to a new structure utilising as far as possible 



