SEA-FISHERIES LABORATORY. 327 



is in Cardigan Bay, and perhaps also Carnarvon Bay. So far 

 this spawning ground has not been found, but I hope to make 

 a search for spawn next season. 



In future seasons I hope to obtain larger samples of fish 

 from the various places along the coast, with a view to 

 discovering how far this grouping of the present samples is 

 justified. 



If we adopt this grouping, and regard the trawled herring 

 separately, we shall find that there seems to be a significant 

 difference in the mean as regards most of the measurements. 



D. Here the 142 fish represented by the first lot of 

 samples, which I shall in future term the "inshore fish," 

 give a mean percentage of 51-74, with a standard deviation 

 (a) of 1-27 and a probable error (E) of + 0-07. (All percentages 

 are percentages of T. cd., as noted above). The trawled fish 

 have a mean of 52-81, a = 0-98, E = ± 0-05. Thus the 

 difference in the means is 1-07, or more than fifteen times the 

 larger E, and is therefore probably significant. If we adopt 

 the formula {^/ Ey + E.*) for the " standard error," this gives 

 a value of 0'08 ; thus the difference of the means is more than 

 thirteen times the standard error. 



V. The inshore fish have a mean of 55-22, a = 1-07, 

 E = ± 0-06. The trawled fish have a mean of 55-64, a = 0-91, 

 E = + 0-05. The standard error is 0*08, and the difference 

 in the means, 0-42, is seven times E, and five times the 

 standard error, and is thus also significant. 



A. The inshore fish have a mean of 75-76, a = 1-24, 

 E = + 0-07. The trawled fish have a mean of 75-91, a = 1-06, 

 E = + 0-05. Here the standard error is 0*08, and the 

 difference in the means is 0-15, only twice E, and is therefore 

 probably not significant. 



I. cp. 1. The inshore fish have a mean of 21-58, a = 0-92, 

 E = ± 0-04. The trawled fish have a mean of 22-22, a =- 0-77, 

 E = ± 004. Here the standard error is 0'05, and the 



