272 RAMBLES OP A NATURALIST. 



and finally how all the links in the great chain of 

 creation are held and bound together by one univer- 

 sal whole which constitutes the great end and object 

 of the studies of the naturalist. 



All these causes of depopulation were combined 

 together in the environs of La Rochelle. Every- 

 where the oolitic limestone exhibited its shallow 

 strata, broken in every direction and cut perpen- 

 dicularly down by the action of the waves. At the 

 foot of these cliffs, there usually extended a long 

 line of the same rocks, formed into broad inclined 

 tiers. Even on the most favourably situated points, 

 I found a marine plant which from its colour and 

 plaited leaves has been compared to our lettuce, and 

 which only grows in brackish water ; down to the 

 very zones of the lowest tide-mark, this inauspicious 

 Ulva formed vast beds, amid which the Fucus that had 

 been closely cut looked something like badly grown 

 chicory. One last sign, which was scarcely less un- 

 promising than the preceding ones, made me tremble 

 for the result of my expedition. Long experience 

 had taught me that nothing is to be found in pure 

 mud. Alike hurtful to the eggs and to the adult 

 individuals, it destroys the former by preventing the 

 oxygen from reaching the germs, while it is not 

 suited for the habitation of the latter, which require 

 a somewhat resistant soil through which to carry 

 their passages and galleries. 



Now at La Rochelle the mud invades everything, 

 both the harbour and the bay ; and it is scarcely 

 possible for the sluices to keep a channel deep enough 

 for the passage of trading vessels. Beyond this arti- 



