A HISTORY OF ESSEX 



year to year, so that what was common at one time may be rare at 

 another, and particular species may have ceased to occur in one locality 

 and have established themselves in another. 



In addition to the animals I have collected myself I give the 

 Hydroids, Polyzoa, etc., collected near Harwich by Mr. S. P. Hope, 

 lent to me by Mr. William Cole, and identified by Mr. Walter Garstang ; 

 and those of various groups collected near Brightlingsea by Mr. H. W. 

 Unthank, as described in his paper, ' Natural History Work at Brightling- 

 sea,' published in the ^Journal of the Essex Technical Laboratories, No. 19, 

 April, 1896, pp. 20610. These additions are more especially valuable 

 because they give a number of species in groups of animals to which 

 I have paid little attention. I also give a very complete and well- 

 arranged list of the Mollusca drawn up by Mr. William Cole. 



In concluding this introduction I must express my best thanks to a 

 number of friends who have assisted me in identifying the various species. 

 These belong to so many groups, and my time has been so much taken 

 up with other matters, that I did not feel confident in my own determina- 

 tion. My thanks are especially due to Mr. Walter Garstang, who has 

 examined and named many of the sponges, Ccelenterata, Nemertians, 

 Chsetopoda and Polyzoa. Professor Herdman has assisted me in naming 

 the Ascidians and Nudibranchs. The Rev. T. R. R. Stebbing has 

 examined some of my crustaceans ; and my Sheffield friends, Professor 

 Denny, Mr. Arnold T. Watson and Mr. E. Howarth, have assisted me 

 over sundry animals. I hope therefore that on the whole the names are 

 correct, but fear that some may not be, owing to the want of suitable 

 specimens collected and preserved for this special purpose. The diffi- 

 culties are also apparently increased by the probable existence of varieties 

 differing from the recognized types, owing to local conditions and other 

 causes. In several cases species which at one time were extremely com- 

 mon and in some respects have been well preserved could not lately be 

 procured for exact specific identification. I may also here say that in 

 the Essex district some of the animals are abnormally small, as if dwarfed 

 by unfavourable conditions. In some cases also only single specimens 

 have been found, and it is uncertain whether they are full-grown 

 animals. On the whole there are ten or a dozen doubtful identifica- 

 tions. 



CHARACTERISTIC FEATURES OF THE COAST 



Before describing the various animals it seems to me desirable to 

 give a short account of the chief characters of the coast, along the whole 

 of which I have passed more or less frequently, since they must have 

 such a great influence on the kind of animals found along it. 



My knowledge of the Thames is chiefly confined to the vicinity of 

 Erith and Greenhithe, at both which places I lived on the yacht for 

 some weeks in 1882. Though the free-swimming animals and plants 

 are of much interest, the district cannot be looked upon as marine ; and 

 I do not know exactly how far the influence of fresh water extends, 



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