182 



J. E. G. Raymont 



Mytilus. In the summers of 1945 and 1946 young mussels settled in enormous numbers 

 over North Bay, but they usually did not survive for very long probably because of 

 the soft substratum. The ordinary samplings did not reflect the full extent of these 

 temporary settlements, but special collections made in the summer of 1945 after the 

 spatfall in Kyle Scotnish and in two nearby other unfertilized arms of Loch Sween 

 (Linne Mhurich and Sailean More) demonstrated the richness of the settlement in 

 parts of North Bay (Table VI). Larger Mytilus were not abundant in North Bay; 

 in fact more were present in Sailean More (Table VI). 



Table V 



The percentage of Hydrobia, oligochaetes and chironomid larvae based on the average 



populations for North Bay 



Table VI 

 Abundance of large and small mussels in three arms of Loch Sween, Summer, 1945. 

 Kyle Scotnish is the only fertilized water. (All figures are numbers per m^) 



Of the " other organisms " in North Bay (Table IV), the commonest were Littorina 

 littorea (almost all juvenile), Cylichna, nemertines and occasionally Philine. The 

 slight rise in " other organisms " late in 1945 and 1946 was accounted for almost 

 entirely by young Littorina. Accra bullata occurred in fair numbers in the deeper 

 waters of Kyle Scotnish during 1946, and it appeared in the shore sampUngs during 

 July of that year. 



ZO NATION 



Although the stations were not definitely related to exact tide level, for each transect 

 Station 1 was sited high up on the flat, and the last station (Station 3 or 4) close to 

 low water. Some attempt has therefore been made to relate very broadly the distribu- 

 tion of the more important members of the fauna to level on the shore. 



