25 8 DISCOVERY REPORTS 



S.N. S. gazellae, and as I have remarked (p. 243) mature S. lyra retain two or three teeth on each side 

 at full maturity. Of fifty specimens of S. lyra, all had at least two posterior teeth on each side, and 

 most had three; of thirty specimens of L.S. S. gazellae, sixteen had no posterior teeth, and fourteen 

 had at least one tooth on one side, and in most cases on both sides ; whereas of thirty specimens of 

 S.N. S. gazellae twenty-five had no posterior teeth, and only five retained one tooth on one or both 

 sides (all the specimens referred to here were at advanced stages of maturity). Fig. 16 shows a com- 

 parison of the teeth numbers of both races throughout their size ranges, and it can be seen that the 

 numbers of posterior teeth found in the L.S. race are slightly higher than those found in the S.N. race. 

 In the form of the body, fins, seminal vesicles and corona, the L.S. race appears to be identical with 

 the S.N. race. 



Table 11. ' Very zvarm water ' form of Sagitta gazellae 



(Stages distinguished by J. W. S. Marr.) 



It can be seen from Fig. 8 that the hook numbers of the S.N. race tend to be scattered above 40 mm. 

 total body length, and the size range of the mature forms is from 45 to 65 mm. or 31% of the total 

 size range of the race. The S.N. 5. gazellae living in the northern and warmer part of the Subantarctic 

 tend to mature at a shorter total length than those living in the colder part of the area. Table 1 1 shows 

 the sizes at the stages of maturity given at the beginning of this section, for a typical warm water haul, 

 and comparison with Table 10 a shows the differences within the Subantarctic zone. Fig. 8 shows, 

 however, that up to 40 mm. the hook number and size relationship is the same for all the forms of 

 S. gazellae in the Subantarctic. The differences in size at maturity are probably environmental, and 

 phenotypic. 



In the L.S. race there is a size range at maturity from 71 to 90 mm., or 19% of the total size range 

 (this is considerably less than that found in the S.N. race), and Fig. 15 shows that the variations in the 

 hook number to size range are much smaller, which suggests that there is less variation within the race. 

 The ratio between maturity and size confirms this. The absence of intermediate forms linking the 

 L.S. and S.N. races, and the fact that the two can be distinguished at most sizes suggest that they 



