SOLLITT, ON STRLE OF DIATOMS. 



51 



down to 



50 genuine specimen from the late J. W. Bailey. 



down to 40 oblique striae. 



46 ditto. 



„ 50 cross do. 



60 ditto. 



120 ditto. 



My friend Mr. Lobb is of opinion that the estimate of the 

 striae on the last of those diatoms is even too low, as he 

 thinks they ought to be set down at 140 in the tcVjj^ °f an 

 inch. From all the above remarks I should like to know 

 what we are to call authenticated specimens. And I think 

 the only conclusion we can come to is, that there is here a 

 very wide field for future observation. The above differences 

 in measurements of the various diatoms do not make them 

 the less valuable as test objects for microscopes, but when 

 used as such, the observer ought always to know what he is 

 looking at. 



