184 



TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



August, there is an apparent negative increment in July, 

 a condition which cannot, of course, be natural. The 

 means and the statistical errors of the means are given 

 at the bottom of the table, and it will be seen that these 

 means must be regarded as free from any error of signi- 

 ficance. Now, compare this Table of the length- 

 Length-Frequencies of Age-Group II <? ? in Barrow Channel 

 and Fleetwood Channel in 1909-1913. 





May. 



June. 



July. 



September. 



15-5 



8 



1 



1 



1 



16-5 



13 



8 



5 



4 



17-5 



25 



21 



14 



5 



18-5 



23 



36 



17 



15 



19-5 



12 



27 



20 



25 



20-5 



12 



31 



12 



29 



21-5 



17 



20 



22 



29 



22-5 



4 



6 



22 



27 



23-5 



10 



5 



13 



31 



24-5 



6 



4 



6 



20 



25-5 



1 



1 



4 



10 



26-5 



— 



1 



— 



7 



27-5 



— 



— 



2 



4 



28-5 



— 



— 



— 



1 



29-5 



— 



— 



— 



2 



Mean 



18-42 



19-73 



20-90 



21-98 







Error of 











Mean 



± 0-145 



± 0-10 



± 0131 



± 0121 



Mean error of means = ± 0-124 



Mean probable error of the 

 difference between any two 

 means = ± 0-175 



frequencies of Age-Group II with a similar one for Barrow 

 and Fleetwood Channels. Here we find a very regular 

 increase in the mean length from 18-42 in May to 

 21-98 cms. in September. There are no data for August, 

 but on making a >™raph for the series of means we can have 

 no doubt as to the value for that month. 



