MARINE ANIMALS ON THE ESSEX COAST. IQ 



later years I have found one or two other animals I had never 

 seen before in the district. 



In considering this question it is, however, inipossilile to be 

 sure that certain of the apparent changes are not due to the 

 remarkably local distribution of some animals, and it is possible 

 that the exact locality where they abound may shift somewhat 

 from year to year, owing to a partial migration. As bearing on 

 this subject, I may say that certain animals are very numerous 

 in one particular place, though I have met with very few or none 

 anywhere else over a wide district. In some cases this may 

 fairly be attributed to the very peculiar conditions under which 

 they are found. For example, I never saw a single individual of 

 a Phascolosoma (not yet identified) until in 1899 ^ ^^'t upon a 

 particular locality near Brightlingsea where several specimens 

 may be found in each spade-full of the sandy gravel. In 1900 

 and 1901 I examined this place more fully, and it seems to me 

 that this unusual abundance in one part and absence elsewhere, 

 close at hand, is due to the peculiar local conditions ; since the 

 Phascolosoma seem to occur only where this sandy gravel is kept 

 constantly soft by salt water draining out through it, when 

 the tide is low, which occurs only in one part, at a particular 

 level, 



There is a locality in the Orwell, a short distance below Pin 

 Mill, usually at about the level of half tide, but perhaps varying 

 with the season, where a species Synapta occurs so abundantly 

 that specimens may be collected out of the mud by dozens ; and, 

 yet, I do not remember seeing a single individual elsewhere along 

 the coast. I cannot understand why this should be so, unless it 

 be due to the percolation of a certain small amount of fresh water 

 from the adjoining shore, \vhich in this particular part is fringed 

 with reeds. In 1901 I could not find a single specimen. In the 

 Deben also, near Waldringfield, I have been able to collect in 

 less than an hour more specimens of Pnapulns candatus than I 

 could obtain in weeks in any other place along the coast ; and 

 yet I cannot even suggest a reason for this, since there do 

 not appear to be any conditions not met with in many other 

 localities. 



So far most of the animals referred to are more or less fixed, 

 or probably do not move far, but there seems to be an equally 

 great variation in those which, like Medusae, float with the tide 



