30 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



Part I. Life History axd Habits. 



PAGE. 



The Spawning Season 30 



The Free-Swimming Period 32 



The Attachment Period 34 



The Commencement of Burrowing 35 



Growiih and Age at Sexual Maturity 36 



Part II. Questions of Economic Importance. 



Pliysical Causes of the Depletion of Our Clam Flats 37 



Natural Enemies of the Clam 38 



Methods of Increasing the Yield of Clams 41 



Transplanting 43 



Rate of Growiih 54 



Results of Experiments in Transplanting 63 



PART I. LIFE HISTORY AND HABITS. 



THE SPAWNING SEASON. 



The eggs of the clam, which are extremely minute, are extruded 

 from the siphon, or snout, of the female clam into the water, where 

 they are fertilized by sperm which the male clam extrudes in a simi- 

 lar manner. 



The spawning season proper extends throughout the latter part 

 of May and the whole of June, and sometimes into the first of July. 

 At this season the great majority of the eggs are laid. 



Mature clams which were examined on the 8th and 12th of May, 

 1899, were found to have their sexual organs full of nearly ripe 

 sexual products. On the 18th, and again on the 20th, artificial fer- 

 tilization was attempted, and, although only from ten to twenty 

 per cent, of the eggs were found to develop normally, at no time 

 of year has artificial fertilization of the clam been more success- 

 ful. These results were confirmed in the following year. This, 

 and the fact that the swimming young were found at this season, 



