436 DR. H. C. SOEBT ON SOME SPECIES OF NEREIS 



the evening of Sept. 9tli, 18S9, at Queenborougli, where numbers 

 Mere swimming about us. Unfortunately only four specimens 

 were preserved, since I expected to collect more the next day ; 

 but thougb I "carefully looked, for them in that and subsequent 

 years, I never saw another. I also never found one in the mud, 

 and do not know exactly where they or the Nereis form live 

 permanently in the district of Queenborough. Some of the 

 specimens are small, being only two inches long, and one differs 

 so much from the re&t that at one time I looked upon it as a 

 different species. 



The case of N. Dumerilii is still more remarkable. I have lived 

 several wxeks, nearly every summer, for many years on the Stour 

 and Orwell, and thought carefully looking out for anything 

 swimming near the surface, I do not remember seeing a single 

 specimen of the Heteronereis except on July 16th, 1898. When 

 I went on deck at 5 a.m. in Harwich Harbour, great numbers 

 were swimming around as far as could be seen, and I was led to 

 conclude that they extended over such a wide area, that possibly 

 the total number was something like a million. None could be 

 seen two hours later. They were of small size, the largest caught 

 being not quite an inch and a half long. The remarkable fact is, 

 that such numbers should come to the surface at nearly the same 

 time, over a considerable area, and swim about for a iew hours 

 and suddenly disappear without any apparent cause. As far as 

 I and Professor Denny have been able to make out, all were 

 males, and I did not see any ova voided from the considerable 

 number of specimens collected and kept alive in sea-water for 

 several hours, when all died, though caught and treated with 

 great care. A number of specimens kept for a considerable time 

 in a large aquarium passed into the Heteronereis state, but were all 

 dead when first observed, and I have no evidence that they lived 

 long in that state. I have, however, kept alive for weeks or 

 months a number of specimens not in the Heteronereis condition 

 and observed their habits. Put into a glass of sea-water they 

 very soon secreted a semi-transparent tube, which they sometimes 

 deserted and formed another. I kept some with a moderately 

 large piece of JJlva latissima. In this they secreted a tube open 

 at both ends, from which they came out when disturbed and 

 went back again. They had nothing to feed upon but the JJlva., 

 which they evidently eat, and their excrements were manifestly 

 pieces of undigested JJlva. One, however, grew up to be a fine 

 specimen full of eggs ; and one day, when disturbed, it wriggled 



