438 DE. H. C. SOEBT OK SOME SPECIES OF NEREIS. 



In addition to the three cases already mentioned, I saw a 

 number o£ Heteronereis, probably of N. Dumeinlii, swimming at 

 the surface in the Colne at higb water on the evening of May 

 23rd, 1885, and also a large species in the Orwell, probably 

 N. longissima, at high water when fine and hot on May 24th, 1889 ; 

 but no specimens were caught so as to make me sure of the 

 species. 



On the whole, then, during several months each year in 

 summer for about twenty years, I saw only five cases in 

 which large numbers of Seteronereis, certainly of two species, 

 were seen swimming at the surface, or about one case for each 

 species in eight years. Of course I was not constantly on the look 

 out, and cannot say what happened during the night or when 

 the sea was rough, and I was not always in places where it was 

 likely to occur. Taking all these things into consideration, it is 

 quite possible that this simultaneous surface-swimming in large 

 numbers may occur every year. It evidently may. take place in 

 the early morning, at midday, or in the evening, and in the early, 

 the middle, or the late part of the summer months. When it 

 does occur, it is such a striking spectacle that it seems worthy of 

 being recorded. Unfortunately I have never been able to observe 

 any facts which afi'orded a satisfactory explanation of the occur- 

 rence. My observations agree well with what has been seen at 

 Plymouth. Dr. Allen informs me that in April 1885 numbers of 

 the Heteronereis of Nereis longissima were seen by Dr. Jonathan 

 Herder, but nothing of the sort in later years. The Nereis form 

 is found in the mud at Salcombe, of about the same size as in the 

 Orwell. 



Nereis diversicolor occurs more or less abundantly in all the 

 estuaries of Essex, Suffolk, and Kent. In preparing specimens 

 for permanent mounting, I have been much struck with the 

 remarkable difference in behaviour of those obtained in diff'erent 

 localities. In St. Osyth Creek they abound in the mud left dry 

 when the tide is down, and when kept in sea-water to which a 

 few crystals of menthol were added the animals were soon stupi- 

 fied, and after a while did not revive when restored to water free 

 from menthol, but died. In the mud of the Crouch near Burnham 

 this same species is so rare that few can be obtained in the course 

 of several hours. On keeping these with menthol, it seemed to 

 have little or no effect. Chloral hydrate also failed to kill them, 

 and to do this I had to use such a very poisonous substance as 



