54 



matter contained therein after the manner of the earth- 

 worm on land. Darwin has shown what an enormous 

 amount of soil is passed through the bodies of earthworms 

 during- this feeding and how the lower layers of the soil 

 are gradually transported to the surface by this agency. 

 I have elsewhere # described how the same work is being 

 carried on by the lug-worm on the littoral and on the 

 sea-bottom wherever muddy sands occur. Indeed in 

 Europe the vermicelli- like castings of this worm are 

 familiar to every visitor to the sea shore. In many cases 

 lug-worms perform a useful function in aerating and 

 cleaning the foul under layers of sandy beaches especially 

 wherever quantities of sea-weeds are cast ashore and 

 covered with sand ; in Arcachon oyster parks they cause 

 trouble by bringing mud to the surface from below the 

 well-consolidated superficial layer formed by the parker 

 with trouble and expense. If a large number of these 

 worms are at work in a park the amount of mud brought 

 up and spread over the surface is very appreciable and so 

 slowly and quietly does the damage progress that many 

 parkers actually are not aware of the importance of this 

 source of the mudding of their ground. 



The last group of passive enemies is that of the 

 sea-weeds. Various species are incriminated, acting in 

 differing manner. Some envelop the oyster in stifling 

 swathes, others buoy it up and enable the waves to carry 

 it away ; some by the luxuriance of their growth lessen 

 the rapidity of currents over the parks and cause an 

 increase in the amount of mud deposited ; another class 

 cause loss to oyster culturists by the decomposition of 

 their fronds when stormy weather uproots them in mass 

 to Hing in heaps upon the oyster-strewn surface of the 

 parks. The greatest harm is wrought by the operation 

 of the two first named factors. The sea-lettuce {Ulva 

 lactuca\ and the tufted red algse termed "bouquet" 

 at Arcachon (Ckondria tenuissima and Hypnca musci- 

 formis) are the worst offenders among the weeds whose 



* "Journal of Mar. Zoology and Microscopy," p. 27, Vol. I. 



