Further Notes on Frustulia Saxonica. By W. J. HicMe. 123 



I may here remark that Dr. Woodward has altogether mistaken 

 the purport of what I said. I questioned but httle the possibihty 

 of his faihng to resolve this or that series of difficult striae with a 

 double-nosed yVth. I also quite as little questioned the amount of 

 inference he might draw from so large a number as two slides, 

 being mindful of the old proverb, 



" But when one's proofs are aptly chosen, 

 Two are as valid as two dozen." 



What I said, or intended to say, was this, that I fairly believe I 

 have spent more hours in the study of Frustulia Saxonica than 

 Dr. Woodward has spent minutes, and that, during my residence in 

 Germany, I had carefully gone over more than five hundred slides 

 of Frustulia, and out of that number had selected two so coarsely 

 marked, as to be easily resolved with a medium power.* And I 

 say now that, if any gentleman present will give himself the trouble 

 of calling upon me, 1 will undertake to show him the longitudinal 

 lines on either of those two slides, and that too without any sus- 

 picion of "diffraction phenomena." Within the last few days 

 I have purchased from Mr. Wheeler a third coarsely marked slide, 

 which also allows its longitudinal lines to be easily resolved. 



As for Dr. Woodward's new criterion for distinguishing the 

 real from the visionary lines, I would observe that, though it may 

 be new, it certainly is not true ; for I will undertake, in the sight 

 of the gentleman who may visit me, to play the very same tricks 

 with undoubtedly real lines that Dr. Woodward has with what he 

 considers to be spurious lines, and will select for the purpose some 

 diatom well known to all of us. Herr Seibert tells us that very good 

 objectives are required to show the longitudinal lines. Dr. Wood- 

 ward, on the other hand, has made it abundantly evident that very 

 moderate objectives suffice to play diffraction tricks. 



I shall not here raise any question as to lenses employed : the 

 " personal equation " also need not detain us ; for we are all aware 

 that all microscopists have equal skill : it is only their lenses that 

 differ; that is to say, every man has a better one than his 

 neighbour. 



" 'Tis with onr lenses as our watches ; none 

 Are just alike, yet each believes his own." 



Much also still remains to be learned, even about diatoms, and 

 it is evident that Dr. Woodward has not learned it. 



It has ever been held to be a wholesome exercise for every man 



* To give an insta,nce in point : on Moller's Probe-Platte may be found a 

 specimen of what MoUer, with his characteristic felicity of nomenclature, calls 

 " JsHtzschia ctirvulc." On my Moller's Probe-Platte this diatom, either from the 

 awkward way in which it is placed on the cover, or from the inherent difBculty 

 of that particular shell, has given me more trouble than any other on that slide. 

 And yet, on a sli<le of the very same diatom, given to mo by Mr. Kittoii, I can 

 readily resolve the frustuks, one after another, with an ordinary J-inch. 



