THE DIATOMS OF GUERNSEY. 



BY MR. E. D. MARQUAND, PRESIDENT. 



Most persons who have made an intelligent use of the 

 microscope know what Diatoms are ; but there are many who 

 have admired the exquisite beauty of their forms and mark- 

 ings without having any distinct idea of the exact position 

 they occupy in the system of nature. They are plants, it is 

 true, but of all plants they are the most unplantlike ; and 

 anyone observing for the first time the peculiar spontaneous 

 movements of these tiny organisms would certainly assign to 

 them a place in the animal kingdom, as indeed did all the 

 best naturalists down to comparatively recent times. 



The Diatomacece, or Diatoms as they are more usually 

 called, are very near relatives of the Seaweeds proper, for they 

 constitute one family of the unicellular algce closely allied to 

 the Palrnellaceoe, of which probably the two most familiar 

 examples are the half-powdery, half- slimy green coating which 

 spreads itself over every damp wall, and the purplish spots, 

 resembling wine stains or blood marks, which cover the 

 ground in moist corners of greenhouses and gardens. 



Everything that is known about these little plants has been 

 learnt through the medium of the microscope, because they are 

 all exceedingly minute, the very largest among them being 

 scarcely discernible by the naked eye ; whilst a multitude of 

 species require a very high magnifying power to render them 

 visible at all. Frequently, however, they occur aggregated 

 together in countless myriads, so that their presence is at 

 once noticeable by the deep coffee-brown film which they 

 form on submerged stones or wood, or on the surface of the 

 mud in roadside ditches and rain puddles, especially in early 

 spring. 



Of all organised beings Diatoms are the most widely 

 distributed, being found in a living state wherever there is 

 standing water — fresh, salt or brackish — from the equator to 

 the poles ; and immense tracts of country are composed 

 almost entirely of their fossil remains. Plenty of information 

 about these very curious little organisms may be found in every 

 work treating upon microscopical objects, and therefore it is 



