90 



SPIRAL TWLST AND OPT. ACTIVITY 



It was found that after having been fed for a prolonged 

 time on carrots tlie typical, dextrally twisted individuals 

 practically did not change their weight, while, under per- 

 fectly identical conditions, the sinistrally twisted snails 

 considerablv decreased in weight (cf. Figure 8). 



320 - 



300.- 



260 - 



240 - 



220 - 



10 



20 



30 



40 



50 



60 



Fig. 8. Change in weight observed in the dextral and sinistral forms 

 of the snail Fruticicola lantzi when they were fed for a long time on 

 carrots. Abscissae: Time in days; Ordinates: Weight in milligrams. 

 (From Gause and Smaragdova, 1939.) 



In the study of the behavior of Fruticicola in starvation 

 it was observed that the sinistral individuals lost weight 

 more rapidly and died off more quickly than the dextral 

 forms (cf. Figure 9). 



The relative weakness of inverse left spiralled indi- 

 viduals is evident in the three series of experiments. 

 Similar results were obtained also in the study of the 

 loss of dry weight. 



