116 



The Naturalist. 



After very high tides I have sometimes found, washed np on the 

 river banks, fragments of exclusively marine algae, such as 'Plocamium 

 coccinemn^ together with Sertularia and other marine zoophytes. A 

 careful examination of the diatomacefe which are plentiful on posts and 

 stones in the river would no doubt bring to light many estuarine 

 forms. Mr. Hunter has kindly furnished me with a short list of 

 diatoms observed by him in the river Ouse at Goole^ among which is 

 one brackish water form, Cymbella gadroides. Marine diatoms 

 belonging to quite a different category may also be found — viz., 

 those derived from Peruvian guano, and washed by the rain off the 

 surface of cultivated fields : ^^ e., Actinocyclus Stephanodiscus, and 

 A. etnpodisctts. 



On the marine fauna of our neighbourhood I am not in a position 

 to say much. Of mammalia the bottle-nosed whale and other cetacea 

 of the porpoise tribe occasionally come up the river, and do much 

 injury to the fishermen. The seal appears to have been found in the 

 Ouse in the time of the Danish colonization of England, for the name 

 of Selby is translated by the' monk who wrote the history of the 

 Abbey in 1184, " FUuU marini villa!'' — the town of the sea-calf or 

 seal. 



Of birds, the common tern and several species of gull are very 

 common with us. 



Of fishes which live partly at least in the sea, the following are 

 met with ; — the salmon, the sturgeon, the flounder, the cucumber 

 smelt, the sea eel, and the lamprey ; the latter fetches a high price 

 from the Dutch fishermen as a bait for cod. 



Of the lower forms of animal life the waters of the Ouse appear 

 remarkably destitute, partly owing to the rapidity of the tide, and 

 partly to the muddiness of the water, which makes it difficult to see 

 the forms which really may be present. I have never seen a mollusk 

 of any kind in the Ouse, and Crustacea are few. A number of the 

 ciliated infusoria closely allied to Vorticplla, but growing in colonies 

 on a branched cartilaginous polypidom, is frequent on stones at 

 extreme low-water mark. 



With a view to learn how far the sea-water reaches up our rivers, 

 I have made several experiments, the results of which are given in the 

 annexed table. Of course the proportion of sea-water present at any 

 given time in the river will depend on various circumstances, being 

 greatest at high water, at spring tides, and in seasons of drought, 

 when comparatively little fresh water comes down from above, 



