REPORT OF COMMISSIONERS OF INLAND FISHERIES. 257 



the young animals are submitted. It is a recognized fact that the 

 diatoms multiply most freely in regions of greater light intensity. 

 This fact is apparent when observations are made upon several 

 groups of lobsters under different conditions of light intensity. In 

 relation to this point we have made observations upon three groups 

 of lobsters in the fourth and fifth stages, confined under conditions 

 of (1) semi-darkness or twilight, (2) very slightly subdued sunlight, 

 and (3) full sunlight. It was very evident that the lobsters confined 

 in an open car with practically no shade accumulated by far the 

 most profuse growth of parasites, while the lobsters kept in twilight 

 were, in every case, quite free. Those kept in slightly subdued sun- 

 light had a more profuse growth than those maintained in the covered 

 cars, but not nearly as great a growth as that on the lobsters in 

 the open car. 



After having made numerous observations on developing lobsters 

 at Woods Hole, Gorham also believes that the abundance of parasitic 

 growth is partially dependent upon the degree of light intensity to 

 which the young lobsters are subjected.* 



These few observations at least indicate the advisability of con- 

 tinuing this definite line of experimentation, not only upon the adoles- 

 cent lobsters, but more especially upon the larval stages on which we 

 know the variations in temperature and food supply have the greatest 

 effect. 



*F. p. Gorham, U. S. Fish Commission Report for 1903, p. 175. 



