RHYTHMICAL MOVEMENTS OF LITORINA. IIQ 



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Mit-nkuri 'oi found that the routine of tin- -urface scatters 

 the -nail- .IIKJ th;it the\ m-vt-r crawl on dry urface-. He al-o 

 stated that Litnriua cxi'^Ha lie-itated mi entering the water and 

 con eluded that their oscillations with the tide- \\< -re due to photo- 

 taxis. In thi- connection tin- writer found that the -nail- 

 he-itated a- n ui cli on leaving the \\ater a- they did on entering ii . 

 Tin- fact, taken in comieciiim \\ith -e\eral of my e\|)eriuient - 

 and e-pe<ially tho-e on -urface tension, -hnw that the < ! i~i-r\'ed 



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he-it. ition \\a- due to the <-t'|. -he -urlai > tilm ot \\ater and 



not in photoiaxi-. 



liohn '05 .'1- IK hide- that ]>lx>in.i\i-. i- the important 



lai tor \\lmli determine- the "-< illatory mo\fmeiit- o| Litorinn. 

 Hi states thai !.ilrin.i nul. nd ///;.<; h.i\e lor all 



their li\e- liei-n desiccated a^ain and av;a;n. and \\heii |. laced in 

 (|iiiet aijii.uia. all three -|>e(ie- retained .1 period ol' rh\thm 

 -\ IK hioiimi- \\ith the tide- and la-tin^; liom thirteen hour- to 

 loin it en d.i\ -. M\ oli-ei \ .ition- -hdu th.it l.ilorhni lit" <; do, ~ 

 not ha\ e -IK li .in i -laNi-hed rh\ thin. 



Ilie l.eha\io|- .) , mi in e\| n-i inieiit 2 i- -tittK ieiil to -ho\\ 



th.it the "directive foi in their rh\ thmical nio\i-nieiit- 



-\ IK hi i- \\ iih tlii tide- i- t he ill m o! \\ater ami not phototaxi-. 



\l-o the fact, lli.il onl\ -n.iil- oil \erlic.il -url'.ice- |iet\\eell the 

 I id 1 1 mark- ha \ e o~eill.it or\ movements, shows thai the direct i\ r 

 force i- not phototaxi- lu-cau-r man\ -nail- on flat hori/i nu al 

 -ml .mid ciaul to t ' arlace and de-cvnd to 



the base of the -tone. l\-pecia'l\ the ol p-er\ at ion- made during 

 dark niuhl- a- \\ell a- maiix other (\perimetil- alieadx cited 

 indicate that Molm'- \ i< \\ i- nnteiiaMe. 



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Ill ( -oiu lii-ion. theii.it a|>pear- that -ulmier.ued indix idu;'.!- of 

 Tina litorcn ciaul almni on i it random, perha|>- 



in search ol looil. The\ ne\ er cra\\l on dr\ -url.ice- and con- 

 -e|Uentl\ are not found above the h ; ;Ji-tide mark. When the 

 tide ri-e-. the en\ ironnii'iit i- temporarily enlarged and con- 

 sequently man\ -uhmer-ed -nail- on more or less vertical surfao - 

 1>\ mere chanci will crawl up higher. 



