The Hard Clam 327 



about the first of November, and does not begin again 

 until about the first of May, reaching its maximum in 

 August. The precise time*when growth ceases in the 

 cold waters of the northern coast varies with the weather. 

 When November is unusually mild and warm, there is 

 some growth, but it is not extensive. There appears to 

 be no growth after the first of December in any year. 

 There is every reason to believe, however, that farther 

 south the growing season is longer than in New Eng- 

 land, and that where it never becomes cold, as in the 

 Gulf of Mexico, it is continuous. 



Few figures showing the percentage of increase in 

 volume in these experiments are yet available, but it has 

 been found that under very favorable conditions the size 

 of the " little neck " — which is about two inches in 

 length — is attained in a little more than two years after 

 the Qgg is fertilized, but on some of the less favorable 

 beds where eel-grass had prevented the flow of water, 

 it was estimated that as many as eight years would be re- 

 quired to produce a two inch little neck. It is believed, 

 also, that quahaugs more than three inches long are at 

 least four years old, and in cases where conditions have 

 not been favorable, more than that. Thus it is not pos- 

 sible to make a statement concerning the growth of 

 Venus that will apply in all cases, because so much de- 

 pends on local conditions. In a general way it may be 

 stated that the average rate of growth is not so rapid as 

 that of Mya, but more so than that of the oyster in cold 

 northern waters. 



As in all previous clam experiments, the most im- 

 portant condition governing growth was shown to be 

 the advantage of a current of considerable strength. 

 Doubtless this is true with all bivalves. In certain fa- 



