i7 



ON THE VARIATIONS IN NUMBERS AND 

 HABITAT OF MARINE ANIMALS ON THE 

 COAST OF ESSEX DURING THE L^ST 

 TEN OR TWELVE YEARS. 



By H. C. SORBY, L.L.D., F.R.S. F.L.S. &c 



During the last ten or twelve years I have spent a good deal 

 of time in collecting marine animals along the coast, and in the 

 estuaries, of Essex and the adjoining parts of Suffolk, as they 

 were floating near the surface or by using a dredge or small 

 trawl, or by examining the mud or shores exposed at low water ; 

 but paying little attention to such as are less than ^-inch in 

 length. In doing this, I have been much struck by the great 

 variations that have occurred from year to year, and with the 

 remarkable contrast between what I now find in some localities, 

 and what I found lo or 12 years ago, or even more recently. 

 Some of the changes may be, and probably are, of a temporary 

 character, and the original conditions may be restored in years to 

 come ; but some seem as if likely to be permanent. In the 

 earlier years I did not expect to be in the district so long and so 

 continuously, and never anticipated that I should witness any 

 striking changes, and so unfortunately I omitted to take such 

 detailed notes as would now have been very valuable. It was 

 only by degrees that the great extent of the changes became 

 apparent. In any case it now appears to me desirable to put 

 some of the facts on record, since they may be of much interest 

 in years to come. 



I have not noticed any material change in the number of 

 some animals. Of these I may mention the Common Shore 

 Crab (Carcinus nmnas), the Hermit Cral) {Pagitriis hcvnhardus), the 

 common Neveis (N. vevsicola), Nepthys hoinbevgii, Arenkola marina, 

 Sahella pavonia, Lanice conchilega, Cirratultis cirratus, Doris pilosa, 

 Echinus miliaris, Solaster papposus, Astenas nibens, Ophinra texturata, 

 Ophiothrix fragilis, and several species of simple and compound 

 Ascidians, such as Ascidiella virginea and aspersa, Ciona infestiualis, 

 done grossularia, Molgula arenosa, Botrylloides ruhrum and leachii 

 and Botryllus schlosseri and polyclyclns. 



There has, however, been a great change in the case of some 

 other animals. I do not take into account such as are so rare 

 that very few specimens have been seen, since in such cases tog 



