282 THE DIATOMS OF GUERNSEY. 



I made in that way at Cobo in September, 1889, yielded 

 sixty-eight species. Dredgings and surface skimmings would 

 most certainly produce some good things, but I have done 

 nothing in that way, though Dr. Wallich adopted both means 

 with gratifying results. Brackish pools hardly equal in rich- 

 ness and variety those in the south of England, perhaps 

 because the water is too salt, but most probably because these 

 pools are for the most part contaminated by the drainage of 

 highly-manured land, or by cattle. The fresh water species 

 are fairly represented, considering the entire absence of 

 sphagnum bogs in Guernsey, but for the reason just given 

 they are found but sparsely in many promising stations. 



Up to the present time no trace of fossil Diatoms has 

 been found in the island. I have on many occasions prepared 

 and carefully examined samples of various deposits submitted 

 to me by my geological friends, hoping to find indications of 

 diatom life at an early period, but not a vestige has been 

 detected. 



A certain inconsistency in the annexed list requires a 

 word of explanation. Whenever possible the names employed 

 are those given in that classical work, the Synopsis of William 

 Smith, the father of British Diatomology, but the order 

 followed is not the one adopted in that work. Even in this 

 small island many species and not a few genera have been 

 found which were quite unknown to Professor Smith, and 

 therefore it has been thought advisable to follow a more 

 recent arrangement in order to locate satisfactorily these 

 newly discovered forms. The classification of the present list, 

 therefore, is that of the last edition of Pritchard's Infusoria 

 (1861), which still remains the best descriptive text book of 

 the Diatoms of the world, both recent and fossil. During the 

 last thirty years, however, a multitude of new species have 

 been described both in England and abroad, so that a com- 

 plete revision of the entire class is greatly needed. 



A word in conclusion as to the present list. The fact 

 that only a solitary valve or perhaps a few scattered frustules 

 of any species have occurred here must not by any means be 

 accepted as certain proof of the rarity of that species in the 

 island ; it is quite likely that it will subsequently be found 

 plentifully in some other spot, or under more favourable 

 conditions. Certain species which occurred very sparingly 

 indeed in Dr. Wallich's gatherings have been found by me in 

 considerable abundance, and vice versa. 



The total number of Diatoms now recorded for Guernsey 

 amounts to 322 species, besides a small number which, being 



