326 



cellulose, and hemi-cellulose constituents of wood. An indication of digestion of the 

 cellulose content of wood was obtained in the following way: The fecal pellets from 

 a test block infected with Limnoria were allowed to collect in a jar of sea water. A 

 portion of the same test block was removed by a fine-tooth file to serve as a standard. 

 The iodine-zinc chloride reaction was used to compare the cellulose content of the 

 two, by micro-chemical methods. The blue color resulting in the cellulose constituent 

 of the wood is due to the formation of amyloid, and its reaction with the iodine. In 

 the case of a yellowish wood such as Douglas fir the resulting color is, of course, quite 

 green. In all cases the wood was examined microscopically, and only fibers or pieces 

 of wood approximately equal in size were compared. It was found that the wood 

 fibers always gave a considerably darker color reaction than those fibers contained 

 in the fecal pellets. Some of the fecal pellets were ground up with glass in a small 

 mortar, in order to remove any possible coating of mucus which might prevent the 

 action of the reagent. A slightly darker color was obtained than with the normal 

 fecal pellets, but a very considerable color difference between the wood fibers and fecal 

 pellets could still be noted. 



In order to determine whether or not Limnoria is able to utilize pure cellulose, 

 about 25 organisms were placed in a jar of sea water containing two small sheets of 

 a high grade of filter paper. Another similar jar was maintained as a control. The 

 capacity of the jars was three liters. Both jars were cooled from the outside by running 

 sea water. The organisms in the jar with filter paper lived two months and twelve 

 days, only five surviving this long, however; they were still alive at the time the 

 experiment was discontinued. The organisms in the control jar without filter paper 

 were all dead at the end of the seventh week. There were thirty organisms in this jar. 



In a number of places the filter paper was found to be gouged out over an area 

 about equal in diameter to that of the body of Limnoria. The fecal pellets also showed 

 clearly the fact that the filter paper had been ingested. It therefore appears probable 

 that Limnoria is able to digest cellulose and utilize it for its maintenance. This ex- 

 periment is regarded as preliminary in nature, however, on account of the limited 

 number of organisms involved. 



The Distribution of Limnori.\ in S.\n Fr.\xcisco Bay 



The distribution of Limnoria in San Francisco Ba>' is shown in the frontispiece. 

 In general, it may be said that the organisms occur in all portions of San Francisco 

 Bay proper where wood is a\-ailable for their attack. Damage occasioned by them 

 is severe along the San Francisco and Oakland waterfronts, at Sausalito and Tiburon, 

 and at the Dumbarton Bridge at the southern end of the bay. They are somewhat 

 less active at Richmond, and become progressively less active above this point. At 

 Point San Pablo and Point San Pedro damage to untreated piling by Limnoria pro- 

 ceeds very slowly, and beyond these points, in San Pablo Bay, it is practically negli- 

 gible. On the west shore of San Pablo Bay occasional e\'idences of work and living 

 organisms have been found as far as China Camp, a fishermen's colony about three 

 miles beyond Point San Pedro. On the east shore they have not been found beyond 

 Point San Pablo. 



There has been some question whether the uppermost limit of the distribution of 

 Limnoria is determined by the factor of lowered salinity, or merely by the absence 

 of whar\-es and landings along the shores of San Pablo Bay for some miles above its 

 entrance. The progressive decrease in the activity of this organism in the upper 



