2 7° Transactions of the Royal Microscopical Society. 
Note, speak generally, as Mr. Hickie does, of what “ Dippel and 
others fancied they saw, but specifically of the longitudinal strife 
ot Dippel. My reason for this limitation was, I confess, that I did 
not at the time know that any authority but Dippel bad described 
longitudinal strife on this diatom. So far as Dippel was concerned 
I had not merely his description and his statement of the number 
ot lines he observed to the inch, but the excellent and truthful 
woodcut m his book* on which to form an opinion. This wood- 
cut, moreover, enabled me both then and now to know that the 
specimens I studied belonged to the same species as that which 
Dippel described. 
In m y “ Note,” then, I spoke only of the longitudinal strise 
of Dippel, but now, in response to Mr. Hickie’s letter, I willingly 
express my belief that the longitudinal lines which he describes are 
ot the same character. At the same time I shall be very glad if he 
can convince me, by satisfactory evidence, that this belief is erro- 
neous, for analogy inclines me towards the opinion that in both 
Fi ustulia Saxonica and Ampliipleura pellucida the striae are 
really lows of beads, as is so easily to be seen in Navicula rhom- 
houles, and that, consequently, we ought to be able to see longi- 
tudinal strife when the illuminating pencil has the proper direction, 
if only our glasses had the requisite defining power. 
In favour of his opinion that he has actually seen these longi- 
tudinal strife on Frustulia Saxonica, Mr. Hickie states, in the first 
place, that Herr Seibert showed him in the summer of 1872 “ a 
couple of very beautiful photographs of that diatom, one of which 
exhibited the transverse, and the other the longitudinal lines, with 
far more clearness, sharpness, and distinctness than the printer will 
be able to reproduce the words I have here written.” If I had 
these photographs before me, they might, perhaps, though I confess 
I do not expect it, show me that Herr Seibert has seen somethin 0, 
I have been unable to see, and I must therefore express the hope 
that Mr. Hickie, in return for the package of photographs I send 
him herewith, will take the trouble to obtain copies of them for me 
to study. I hope also that he will obtain copies of them for the 
Eoyal Microscopical Society, to compare with those I send. In the 
absence of Herr Seibert’s photographs, however, I would remark, 
that spurious lines, due to diffraction and interference, can be photo- 
graphed quite as readily as real lines, from which they can only be 
distinguished by observing precautions which Mr. Hickie’s letter 
does not show to have been considered either by himself or any of 
the distinguished gentlemen to whom he tells us he exhibited the 
longitudinal strife in question. 
Mr. Hickie tells us further, that “ In Ehomboides also the 
transverse lines are much closer than the longitudinal, whereas in 
* Op. cit., fig. 103. 
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