HELIOTROPIC REACTIONS — ANIMALS AND PLANTS 



233 



of Areiiicola, Chlamydomonas pisiformis, and larvae of Balanus; 

 the greater darkness indicating the greater efficiency. The two 

 most striking facts to us are, first, that there are animals for 

 which the most efficient part of the spectrum is in the blue. 



Chlamydomonas pisiformis. Dill. 

 Wave lengths in fi/x 



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iTn :i';ii -ii: 'i "i 'I "! "I "I "'i' 1 ^i i l'"1 ■ r > : ■ IfSI ' ma ; i ■ i 



namely Eudendrium and the larvae of Arenicola; and that among 

 the flagellates, Chlamydomonas is most sensitive to yellowish- 

 green, while the closely related Euglena is most sensitive to the 

 blue. 



The second striking fact is that the place of greatest efficiencj^ 

 does not seem absolutely identical in the organisms of the same 



