140 MISS MARION I. NEWBIGIN. 
seasons of the year; they are often hatched from the eggs 
left by the preceding, and then quit the shore as they 
approach adult life; or they may be the young of the true 
shore forms, and then their disappearance is only apparent 
and is due to their conversion into the adult form. 
The classification is, of course, not a strict one, but it 
is convenient to study the shore forms grouped under 
some such heading. It is to be noticed also that the 
classification refers only to the strictly marine forms. For 
those who dishke wetting their feet, the shore contains, 
in addition, many curious and interesting creatures. Over- 
head the birds circle and cry, aud on the shore rocks many , 
species often occur together. If you are content with 
humbler prey you will find that the uppermost rocks, those 
rarely if ever washed by the spray, are crowded with 
interesting forms. Among these are wingless insects, the 
curious springtails, and strangest of all, down the deep 
clefts, a very large ‘slater’ (Ligia oceanica) which 
resembles superficially one of the extinct Trilobites, 
which may perhaps be found fossilised in the same rocks. 
Then there are the sandhoppers, many kinds of beetles, 
ants, and numbers of other animals all to be found above 
high water mark within a very limited area. These, 
however, we shall neglect in favour of the true marine 
forms. 
1. Let us consider first the true permanent residents— 
those adapted for life between tide-marks. Now I need 
not remind you that the most universal and most striking 
characteristic of living things is that they are adapted to 
their surroundings—their environment. We must, there- 
fore, ask what special peculiarities the surroundings of 
shore animals display. We have already noticed the 
abundant food supply, due, in part, to the drainage from 
the land, in part to the abundant growth of weed in the 
shallow shore waters. An even more striking peculiarity 
in our part of the world is, however, the daily ebb and flow 
of the tide. Twice in each twenty-four hours the waters 
retreat and leave bare a great stretch of the shore, twice 
they return, the breakers thundering on the rocks as they 
advance. Sit on the rocks at North Berwick when there 
