SELECTED NOTES. 193 



may be about five feet thick ; towards the north end it is over 

 twenty feet thick. 



It is obvious that out of hundreds of slides I can only send 

 round a few specimens. These shall be chosen so as to show 

 those who know little about diatoms their extreme beauty, both as 

 separate mountings, and as " spread " slides ; the latter will show 

 how the various forms are commingled. A few " test" slides will 

 also be added for those who possess " high powers." 



I need hardly add that those who want to see Diatoms in their 

 native beauty with their endochrome should not fail to get some 

 diatomaceous material from some sluggish stream or marine marsh, 

 and look at them in a drop or two of water on a slide with a 

 cover-glass over, and view them with a j4-\nch objective as they 

 move — vegetables moving ! — they will have a treat. 



If these slides convey to many of our members the same 

 pleasure that for years they have done to me — an old clergyman 

 in weak health — I shall be well repaid. They have been obtained 

 from various sources, mainly from my old friends, E. Grove, Esq., 

 and Major Lang. The former is well known for his Paper on the 

 " Oamaru Deposit " ; the latter as one of the most splendid 

 mounters of "separate" forms. Some of the slides require at 

 least ^-inch objective. 



Many persons give the whole of their leisure to the study of 

 Diatoms ; therefore, though they may be little known to some of 

 our members, those who have taken up the study must be borne 

 with if they say that they find in it a great satisfaction. 



When one thinks of the prodigality of beauty that is around 

 us, and which no eye of man perceives, one sees an inner meaning 

 in the words of Rev. iv. ii — "For T/iy pleasure they are, and 

 were created." 



Description of Slides. 



Heliopelta (Sun Shield). — This is one of the class Actinop- 

 tychus, and one of the most beautiful of the discoid forms. The 

 structure of the valve appears to consist of an inferior layer, con- 

 taining large cavities or areolse, which on the elevated compart- 

 ments of the valve present the appearance of hexagonal cells, and 

 in the intervening compartments, of irregular circular cells ; and of 



International Journal of Microscopy and Natural Science. 

 Third Series. Vol. VI. n 



