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Part III. — Twentieth Anmud Report 



for the combined sexes was 1 54*5 mm. In July the mean size was 

 172*2 mm. for the group with the sexes mixed, and the combined hauls 

 in August comprised ninety females with an average length of 

 189 "0 mm., and seventy- four males with an average size of 156'2mm., 

 the mean for the group being 174"2. 



It is clear from the variations in the averages, and from the curves, 

 that the mean size is not truly I'epresented. The apparent annual 

 increment of growth from the previous or younger series indicated by 

 the averages named is as follows; — 



The difterences in some of these cases are considerable, and may he 

 partly ascribed to the imperfection of the third series, and partly 

 perhaps to its limits not having been accurately determined. In May 

 at Station III. the smaller fishes of the group, as already stated, were 

 absent, and the average was consequently too high. In June there 

 were only three males in the second group, and seven in the third. 



Still older series were represented, but their limits are even more 

 doubtful. In May at Station III. three additional groups appear to be 

 present, the fishes in each consisting exclusively of females. The fii'st 

 of these, or Group IV., comprised thirty-nine sjiecimens, with an average 

 length of 225"8 mm., or 8^ inches; the next contained seven specimens 

 whose average length was 292"0 mm., and the next four specimens with 

 an average size of 337 mm. The annual increments represented by 

 these averages are 42-1, 66*2, and 45 mm. In the August hauls other 

 two series were represented, also exclusively females; one (IV.) com- 

 prised 51 fishes ranging from 215 to 261 mm., and having an average 

 length of 235"0 mm., the other (V.) comprised five from 260 to 289 mm. 

 with an average size of 274"2 mm., or 10J-| inches. The apparent annual 

 increments indicated are respectively 44*2 mm. and 37*2 mm. 



At Station V. the fourth group, consisting of females only, gave in 

 May an average of 211 "1 mm., and the range was from 190 to 241 mm. 

 There were two larger females measm"ing 267 and 312 mm. respectively. 

 In the haul on 16th Avigust the fourth group was represented by seven- 

 teen females with an average of 223*5 mm., and a range from 211 to 

 250 mm.; in the haul on 21st August it was represented by twenty- 

 four females with a range from 212 to 251 mm., and an average of 

 225*3 mm. There were two females measuring 288 and 310 mm., and 

 one measuring 354 mm. The averages given show either that the true 

 limits of these older groups have not been established, or that the 

 groups were imperfectly represented. While a study of the grouping 

 and the curves in a given case appeared to indicate that a certain 

 demarcation was natui'al, another case contradicted it ; and it is 



