HENDRY, ON NAVICULA RHOMBOIDES. 



233 



N. rhomboides, Slide III. — Connecticut (America). 



There are individuals who object to the appellation of striae 

 to coarse exhibitions wherein a finer striatiou is usually 

 ascribed, and who maintain also that upon such coarsely 

 marked diatoms two sets of striation must necessarily exist, 

 could they only be seen, id est, the coarse as already assented 

 to when present, and the finer yet in obscurity ; but although 

 I must oftentimes ere this have seen the finest visible as well 

 as the coarse, I have hitherto no evidence to induce the sup- 

 position of a twofold striation of the kind upon the same 

 frustule. 



Amidst the ordinary objects of our observation in nature 

 she i«, undoubtedly, at times, exceedingly capricious, hence ; 

 why should we hesitate to accord to her a broad latitude in 

 the development of more minute forms, so far surpassing 

 the greater in beauty of design and exquisite delicacy in 

 workmanship as in the diatoms under consideration? 



In the accompanying tabulated measurements it will be 

 observed that no numerical striation bears any definite rela- 

 tion to the magnitude of the shell ; that upon Slide II, 

 Diatom 11 and 16, the smallest registered exhibits only 34 

 striae in "100, while the largest registered thereupon exhibits 

 34 striae in "100 also. 



