On Animal and Vegetable Life in the Water of Leith. 235 



stream or of the lade harboured myriads of even this infe- 

 rior type of animal life, there was hardly a specimen to he 

 had, and this was doubtless due to the more rapid putre- 

 scence of the deposits. Abundance of aninialculae, including 

 the Paramcecia, were found in the Water of Leith at all 

 seasons of the year. 



One curious effect of sewage upon animal life was ob- 

 served by me in the harbour of Leith. Two wooden piers 

 stretch some distance into the sea ; they are constructed of 

 the same kind of timber, and are of the same ao;e. The 

 west pier is not liable to be influenced by sewage passing- 

 down the harbour, as the tide sweeps the sewage from it. 

 and the wood of this pier is nearly eaten through in some 

 parts by the Teredo, a bivalve (Lamellibranchiate) mollusc, 

 which is well known to be destructive to wooden erections 

 in the sea. But the east pier is washed b}^ the sewage 

 water, and apparently from the disengagement of sulphuretted 

 hydrogen, which is specially formed when sewage meets sea 

 water, there is not a single Teredo to be seen at its work of 

 drilling holes in the wood. The sewage in such circum- 

 stances therefore appears to be beneficial in retarding the 

 ravages of this troublesome mollusc. 



Independently of the putrefaction of the sedimentary de- 

 posits, fish might live in water which contained nearly the 

 proper proportion of oxygen, but the water of the Water of 

 Leith from Colt-bridge downwards is almost devoid of oxygen, 

 and fish can no more live in water containing no oxygen 

 than land animals could live in an apartment destitute of 

 air. 



It is worthy of note, as evidence of the state of the Water 

 of Leith, and its incapacity to support the life of fish, that 

 during the summer of 1864 a shoal of young herrings at- 

 tempted to enter the harbour of Leith, and those herrings 

 turned over on account of the foulness of the water, and the 

 majority died upon the spot. 



During the progress of these observations, attention was 

 directed to a green substance consisting mainly of Euglena 

 viridis, one of the Phytozoa, which was observed on the sur- 

 face of the stagnating mud at the side of the Lochrin Burn, 



vol. nr. 2 h 



