Plate VIII. 

 {Top) Skeletons of diatoms; (left) Aiihicodisciis margnritiueous (related to Coscinodisciis Plate I, 

 I and 2); (right) ActiiwptYchiis hcUcpelta (related to .4. uiidtilata Plate I, 3); both about 200 ^x. 

 {Bottom) 'The old microscopists playground'; geometric arrangement ot diatoms and spicules; 



the groups are about 2 millimetres {left) and 3^ millimetres {right) across. 



[Photographs prepared by the author from negatives made in iSy2 by the late J. Ogilvie, tea and 



coffee merchant, Dundee. The original mounting of the arrangement in the bottom right was 



by E. Thum of Leipzig and consists of 329 pieces.] 



