322 



arranged that one-half was in its own shadow. The attack of Limnoria on both sides 

 of the piece was very nearly- equal. 



The fact that Linnwria attacks a pile at all levels from mid-tide down to a depth 

 of 40 feet or more, where it is considerably darker, indicates that there is no effective 

 reaction to differences in illumination. 







' .^ > 





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ii.;>i^Z 



^iwf.^ 









Fig. 133. (1) Untreated Oregon fir fender pile exposed one niontli, July, 102(1, in Municipal Quay, 

 Oakland Estuary. Initial attack of Limnoria. 



(2) Untreated Oregon fir pile in Southern Pacific Oakland Mole. Deeper penetration by 

 Limnoria. 



(3) Untreated Oregon fir fender pile, driven in Oakland Municipal (Juay in 1913, removed in 

 1020. Limnoria attack uncovering Bankia tubes. 



Limnoria shows very definite reactions to any substance into which it may force 

 its claws and so attach itself. This thigmotropic reaction shows itself particularly 

 when the organisms are placed in a clean Petri dish. If there are no other objects 



