^f'l-^I Miiliarl: Sofjilla cdllfurnica fron San Diego Region 105 



under 16 mm. in length is the ganglion greater than 6.75 per 

 cent. Tliis vi.sual evidence is corroborated by the correlation 

 coetlicient, which i.s negative and more than twenty times tlie 

 probable error. Jloreover, examination of the numbers in 

 brackets shows that, when the ganglion is less than 5.75 per 

 cent, the proportion of the popnlation having a ganglion of that 

 length increases with the length of animal, while, when the 

 ganglion is greater than 5.75 per cent, the proportion decreases 

 as the animal increases in length. This becomes especially clear 

 when arranged as follows : 



14 per ceut of animals lS-20 mm. have ganglion less than .5.75 per cent. 

 61 per cent of animals 20-22 ram. have ganglion less than 5.75 per cent. 

 84 per cent of animals 22-24 mm. have ganglion less than 5.75 per cent. 

 93 per cent of animals 24-26 ram. have ganglion less than 5.75 per cent. 



86 per cent of animals 18—20 rara. have ganglion more than 5.75 per cent. 



39 per cent of animals 20-22 mm. have ganglion more than 5.75 per cent. 



16 per cent of animals 22-24 mm. have ganglion more than 5.75 per cent. 



7 |ier cent of animals 24-26 mm. have ganglion more than 5.75 per cent. 



Furthermore, when the average proportional length of ganglion 

 corresponding to each of these groups is calculated, it becomes 

 quite clear that the animal increases in length faster than the 

 ganglion does. Here are the averages : 



7.50 per cent for animals between 12 and 14 mm. 



6.16 per cent for animals between 14 and 16 rara. 



6.33 per cent for animals between 16 and 18 mm. 



6.14 per cent for animals between IS and 20 mm. 



5.58 per cent for animals between 20 and 22 mm. 



5.41 per cent for animals between 22 and 24 ram. 



5.32 ]ier cent for animals between 24 and 2B mm. 



Now if, on account of their small numbei-, we eliminate from 

 consideration those animals under IS mm. in length and examine 

 these averages further, expressing the length of animaLs between 

 18 and 20. 20 and 22, 22 and 24, and 24 and 26 mm. in terms 

 of their averages 19, 21, 23, and 25 mm., the following facts are 

 revealed : 



1. An increase in length from 19 to 21 nmi. is accompanied 

 on the average with a relative decrease in length of ganglion of 

 0.56 per cent. 



