F. S. Wright 133 



Can we, then, take this result as our ideal population factor, as it 

 stands, and can this numerous population be expected to flourish ? In 

 order to determine this point, in view of what is known with regard to 

 the abundant food supply available for the mussel, I conducted the 

 following check experiment. A band of thin iron, Ih" in depth, was bent 

 into the shape of a square foot, in which were placed mussels, "head" 

 end downwards, 2|" in the vertical axis, until the measure was well 

 filled. Sufficient space was allowed for each individual to function. 

 They were then counted, and were found to number 121 (11 x 11) 

 individuals. This result is in close agreement with the rougher totals 

 obtained in natural conditions on the Ro-dclu seed bed. Therefore, such 

 a number can live and thrive on the fishing grounds, and it may safely 

 be taken as the population factor desired. The poor condition of the 

 mussels on the seed beds is due to a special cause, or a combination of 

 causes, which will be considered immediately. 



Such a population obviously cannot be distributed homogeneously 

 over the whole of the fishing grounds, but, even if portions of it have 

 been too thickly restocked, a certain degree of readjustment will take 

 place. The diatoms, and other organisms, vegetable detritus, etc., on 

 which Mytilus feeds are present in practically inexhaustible quantity, 

 and every individual in even a populous colony will be able to procure 

 an ample supply of food material for its needs, unless, that is, badly 

 overcrowded conditions cause the water currents to become obstructed 

 in certain cases. 



I have examined a large number of mussels from the seed areas (more 

 especially those from Ro-ddu Scar, Aberdovey), as well as from the fishing 

 grounds, at different seasons of the year, with regard to their stomach 

 content. Some very interesting, and apparently contradictory facts 

 were noted in this connection, but upon consideration, these will be 

 found to be in accordance with the conditions in which the mussels live. 



I have found, for instance, that the stomach content of the seed 

 mussels (poorly fleshed mussels) is generally equal to, and sometimes 

 greater than, that of individuals from the actual fishing grounds, although 

 scientists and others have not hesitated to call the former starved indi- 

 viduals. Also, the organisms, etc., present were, if anything, in greater 

 variety in the case of the mussels from the scars. This state of things 

 needs some explanation, but this attempt to account for the poor flesh- 

 content of the seed muscles must be regarded as tentative. As the 

 beds at Aberdovey are very sharply defined, I confined these observa- 

 tions to this place, for the most part. 



