320 J. H. ORTON. 



relation to those obtained by Russell will be discussed later when more 

 data are available, 



Anomia aculeata has in several independent experiments been found 

 to attain to an average size for this species and to give larvae on being 

 fertilized at an age of less than four months. Specimens of this age have 

 been taken at various times of the year with the same result, hence this 

 species undoubtedly passes through two and probably three generations 

 within a year. Next to the common mussel this is probably the 

 commonest mollusc on our shores. 



The boring mollusc, Teredo navalis, has been tound to grow to a length 

 of 19-8 cms. in 31 weeks, and made borings in soft wood 28 cms. long 

 with an average width of about 1 cm. It was also found that the gill was 

 alive in specimens obtained a fortnight after the wood in which they 

 were living was taken out of the sea. Thus these animals would be 

 able to live easily during the period during which most vessels would be 

 in dry dock for scraping and painting, hence, as is well known but not 

 always fully realized, it is highly important that wooden vessels should 

 be constantly cleaned to prevent the attacks of this destructive mollusc. 



THE RATE OF GROWTH OF CREPIDULA FORNICATA. 



By means of a grant from the Royal Society a number of special 

 experiments were carried out during the year of 1913 off the Essex coast 

 with the object of determining the rate of growth in Crepidula. For 

 this purpose a floating raft containing shells and tiles was moored at the 

 mouth of the River Blackwater in the expectation of catching the spat. 

 In putting out the raft and taking it in again in the autumn the Directors 

 of the Tollesbury and West Mersea Oyster Company very kindly placed 

 at my service the valuable help of their fishermen and their boats, and I 

 wish here to express my thanks to them for the facilities they gave 

 me in carrying out the experiment. The design of the experiment 

 succeeded, and Crepidula spat was obtained on the raft and on the 

 material placed in the raft, but unfortunately this success was marred 

 by the fact that the raft had probably been touching the bottom of the 

 river a few days when I went to examine it. It is therefore possible but 

 not probable that some of the spat obtained on the raft may have crept 

 on to it. Hence it is hoped to try the experiment again this year. From 

 the position of some of the spat on the raft and on the tiles in it there 

 was no doubt that they had been settled there some time, and therefore 

 before the raft touched the bottom, and as the specimens obtained were 

 all of sizes similar to the smallest sizes obtainable on the grounds in the 



