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NOTE ON NEW DIATOM STRUCTURE. 



By A. A. C. Eliot Merlin, F.R.M.S. 



(Read December 2l$t, 1006.) 



I have lately effected the following resolutions of diatomic 

 structure which I believe to be new, and may prove of interest. 



Melosira clavigera, Grim., var. ; Oamaru. 



The hyaline silex centre of this form is covered with a very 

 beautiful lacework which, although it cannot be described as 

 easy, would probably yield to a really good objective of N.A. 1*3 

 with critical axial illumination. I have completely resolved it 

 with the Zeiss g-in. apochromat of N.A. 1*42, and full cone of 

 Powell's dry apochromatic condenser used in conjunction with 

 Gifford's blue-green glass and methvl-green screen. A specimen 

 of the normal 31. claviyera from the same locality shows fainter 

 perforations of a like kind. 



Melosira marina, Kutz ; Oamaru. 



The centre of this diatom exhibit- similar structure to the 

 above, but finer. 



Melosira biseriata ? Oamaru. 



Moller places a note of interrogation after the species of this 

 form. It has an extremely delicate network pattern all over the 

 large central hyaline area. It is much more difficult than the 

 preceding forms, but has been completely resolved with N.A. 1*42 

 and a large solid axial cone. The 31. clavigera and 31. marina 

 should be examined first, as it would be quite useless to expect 

 any optical arrangement which failed on them to succeed with 

 the 31. biseriata. These remarks, however, should be taken as 

 only strictly applying to the specimens actually examined, it 

 being quite possible that some examples of the species referred 

 to may be found to vary and possess coarser structure. 



With reference to my paper read January 19th, 1900 (Q. 31. C. 

 Journal, Second Series, vol. 7, p. 295), in which I stated that 

 the faint secondaries seen on the upper surface of the hyaline 



