1917J Barrows: Shii^worni in San Francisco Bay 43 



8. In such a bay as that of San Francisco, which is infested in its 

 main portion with shipworms, and in which the movement of the tide 

 is strongly felt in many parts, the borers may be expected to take ad- 

 vantage very promptly eitlier of any variation in salinity which will 

 permit them to invade a previously unoccupied locality or of any 

 change in current conditions which by bringing in a more abundant 

 food supply than formerly will permit an increased rate of growth 

 and of destruction of woodwork. 



9. This unusual occurrence of shipworms in the upper part of San 

 Pablo Bay is indicative not only of the avidity with which such an 

 organism seizes upon every opportunity to extend its distribution into 

 previously unoccupied localities but also of the great importance of 

 even slight and relatively temporary variations in conditions of the 

 environment in determining the limits of the distribution of the species, 

 particularly upon tlie fringe of its range. 



10. It is noteworthy in this instance that Limnoria is not reported 

 to have invaded San Pablo Bay in company with Teredo diegensis, 

 though in other localities in San Francisco Bay, especially in those in 

 which the salinity is somewhat reduced, Limnoria constantly accom- 

 panies the shipworms, and in certain places almost altogether super- 

 sedes them as a wood-borer, as, for example, in the Oakland estuary, 

 where conditions seem, to be less favorable for the teredine borers. 



Transmitted March 9, 1017. 



Bibliography 

 Moll, F. 



1914. (The shipworni; translation.) Naturw. Zeitschr. f. Forst-u. Land- 

 wirtscli., 12, 505-564, 12 figs, in text. 



SiGERFOOS, C. P. 



1908. Natural history, organization, and late (leveloi)nient of the Teredi- 

 nidae, or shipworms. Bull. U. S. Bur. Fish., 27, 191-231, pis. 7-21. 

 Sumner, F. B., Louderback. G. D., Schmitt, W. L., and Johnston, E. C. 



1914. A report upon the physical conditions in San Francisco Bay based upon 

 the operations of the United States Fisheries Steamer "Albatross" 

 during the years 1912 and 1913. Univ. Calif. Publ. Zool., 14, 1-198, 

 pis. 1-13, 20 figs, in text. 



