56 THE BIOLOGY OF THE SEA-SHORE 



observe that Blennies seek clean objects on which to fasten 

 their eggs, and any fresh and hence uncoated object will 

 usually be so covered within twenty-four hours. 



Ecological Succession. — An opportunity to observe the 

 colonisation of a new area by shore forms was provided 

 by the opening of the Kiel Canal, which connects the Kiel 

 Bight with the Lower Elbe and is some 62 miles long, in 

 the summer of 1895. Up till the time of opening and for 

 a short period afterwards the canal contained only fresh 

 water, and consequently supported a fresh-water fauna and 

 flora. The ousting of fresh-water forms from the canal, 

 and their gradual replacement by marine species, has been 

 described by Brandt (1897). Owing to seasonal changes 

 in the amount of water entering the canal and to the periodical 

 opening and shutting of the lock gates, the salinity of the 

 canal water is subject to considerable variation. This is 

 a feature of importance. 



The first phase of the colonisation of the canal with 

 marine organisms consisted in the penetration of plankton 

 and the free-swimming larv'se of coelentera, worms, crus- 

 taceans, and molluscs ; the second phase in the development 

 of such forms, which derived their nourishment from the 

 plankton (no other form of food being present). Up to 

 the autumn of the year in which the canal was opened only 

 planktonic organisms and plankton-feeders were present 

 {e.g. Mysis vulgaris, Mytilus edtilis, Balanus improvisvs), 

 together with such forms as live on the remains of dead 

 organisms {e.g. Gammarus lociista). In the winter of the 

 same year and in the following spring came the third 

 phase, signalled by the entry of animals which prey upon 

 plankton-feeders : starfish, larger Crustacea, fish, etc. Con- 

 temporaneously, other rivals to the plankton-feeders put 

 in an appearance in the shape of species with a similar 

 mode of feeding, so that the mussels, for instance, 

 decreased considerably in numbers. Following almost 

 immediately upon this phase came the fourth : the appear- 

 ance of plants (algse) along the banks. As soon as the 

 algae were present in good numbers other animals which 



