321 



reactive after wliat may be called "woutl star\ation." Tliis d(>e> not apjiear to be 

 the case from the ali()\e experiments. 



In iirder to test the point further, an extract of fine Douglas fir sawdust was 

 made, using sea water as the extracting agent. The mixture was boiled in an ordinary 

 reflux condenser so that the filtered extract was isotonic with sea water. It was not 

 concentrated by evaporation. In order to form a localized center for the diffusion of 

 the extract, a small wad of lens paper was soaked in it and placed in an oblong |)an 

 containing fift\- Linuinria. At the other end of the pan another piece of len> [Kijier 

 was placeil as a control. Although these organisms were quite active and swam the 

 length of the pan repeatedly, they did not exhibit any preference or tropistic reaction 

 toward the lens paper which had been soaked in the wood extract. After three days, 

 the majority were not attracted to either piece of lens paper. There were a few more 

 organisms on the control paper than on the piece which had been soaked in the extract. 



It was thought that the temperature of the extraction might ha\e altered some 

 of the constituents to which Linnioria is sensiti\e. Some sawdust was accordingly 

 placed in the lower half of a thin walled test tube which had been drawn out so that 

 its aperture was reduced about one-half. It was then placed in a pan with a large 

 number of Limnoria. 



The distribution after two days ap|-)earetl to hii\e no rehition to the wood in 

 the test tube. The organisms were generally dispersed throughout the pan. This 

 type of experiment, with minor \'ariations, has been repeated on several occasions, 

 with in\ariabh' negatixe results, which leads us to beliexe that in the case of Limnoria 

 there is no chemotropic response to wood extracti\'es which is an eftecti\e agent in 

 the dispersal of the organisms and the initiation of their attack on wood. 



In order to determine how long Limnoria can exist without wood the following 

 experiment was carried out. Two three-liter jars of sea water were arranged so as to 

 be cooled from the outside by water pumped up from the bay. Thirty-eight organisms 

 were put in each jar. There was no wood of any kind in either jar. In both jars the 

 organisms li\ed for o\er six weeks and were able to swim alioiit when disturbed. 

 At the end of this time a few of the indi\iduals in one jar were dead; in the other jar 

 all appeared to be normal. This abilit\' to li\e without wood for a considerable period 

 is a factor in favor of sur\i\al of the isolated organisms. 



While Limnoria is able to swim for short distances, it d(jes not appear that 

 swimming can account directK' for its distributit)n. The greatest linear distance we 

 have observed an animal to swim is id)out three feet. The swimming tends in a general 

 upward direction and as soon as it ceases the organism rapidly sinks. The tendency 

 to sink rapidh' necessitates a vigorous action of the pleopods, by means of which the 

 swimming is accomplished. The organism swims on its back, in a series of short 

 darts which result in a spiral or irregularly curved path. Such a course would appear 

 to increase the probability of the organism's coming in contact with a pile or other 

 structure while being swept about In' tidal currents. But, as pointed out above, 

 Linnioria does not remain suspended in the water and is only able to keep itself from 

 sinking rapidly by a xigorous action of the pleopods; this fact makes the distribution 

 of unattached Limnoria by tidal currents of doubtful importance. 



In order to determine whether or not Limnoria exhibits any reaction to light, a 

 well soaked piece of pine wood was placed in an aquarium in a vertical position and 

 maintained there by a cross-piece. The \ertical position is essential since wood in a 

 horizontal position accumulates considerable sediment on its upper surface, hence the 

 lower and darker surface would be more likely to be attacked. The aquarium was 

 illuminated from one side, the other sides being blackened, and the test-piece was so 



