203 DISCOVERY REPORTS 



zone and Weddell drift that lie beyond, that are par excellence the principal spheres of hatching of the 

 eggs of this euphausian. Indeed, in so far as the slope waters are concerned, it may well be that there 

 they hatch on the sea bed itself, an inference that as already suggested (p. 184) may readily be drawn 

 from the vertical distribution of the Nauplii at Station 2603, the slope station in Fig. 29 where over 

 400 Second Nauplii and 75 Metanauplii were recorded in a net that came within 50 m. of the bottom. 

 It has been shown then, that in spite of the frequency with which eggs have been encountered in 

 shelf water and in spite of the concentration of them found at Station 540, the production of Nauplii, 

 Metanauplii and First Calyptopes that results from shelf hatching, when compared with the cor- 

 responding production resulting from deep oceanic hatching, is to all appearances negligible to a 

 degree. It still remains to be considered, however, to what extent this disparity, so obviously 

 apparent in the very early larval stages, may be said to be true of the larval production as a whole. 

 The total monthly larval gatherings from vertical hauls made in the shelf waters of the Brans- 

 field Strait, Weddell West, Ross Sea and Bellingshausen Sea, and from similar hauls made in the 

 oceanic waters of the Weddell and East Wind zones are brought together for direct comparison in 

 Table 43. It will be seen from this presentation of the data that, having regard to the total number of 

 stations operated monthly in both shelf and oceanic regions, from January, when the climbing larvae 

 first begin to come within range of our deepest vertical nets in substantial numbers (p. 90, Table 13), 

 to April, the last month in which we have observations in Antarctic shelf water, the productivity of 

 the shelf regions is consistently low, and in general does not even remotely approach the corresponding 

 productivity in the open sea. There is evidence, it is true, of some minor concentration of larvae in the 

 shelf regions in March and April, but since all the shelf larvae recorded in these months were in fact 

 recorded from the Bransfield Strait, and since all except the single Metanauplius in March are essenti- 

 ally surface forms, they need not necessarily have been produced in situ but could have drifted into the 

 strait with the Weddell or Bellingshausen Sea water which, as Clowes (1934) has shown, enters it, the 

 former from the east, the latter from the west. 



Further evidence of the negligible scale of the shelf hatching, again based on the vertical data, is 

 provided by Table 44 in which the disparity in productivity in shelf and oceanic water is shown on 

 a vertical scale. In the construction of this table, which is based on the data from the vertical stations 

 mentioned in the preceding paragraph, the months from which material for direct comparison is 

 available are treated not separately as in Table 43, but as a whole, the production figures, restricted 

 in this instance to the months in which the eggs and succeeding larval stages may be said both 

 severally and by groups to have their optimum range in the plankton, having been obtained in 

 each instance by dividing the total optimum-period-catch of the eggs and the twelve separate larval 

 stages in any particular vertical horizon by the total number of net hauls made during the optimum 

 period at that particular level. Thus (see again Table 43), the optimum range of the eggs and Nauplii 

 has been put at as from November to March, of the Metanauplii from December to April, of the 

 Calyptopes from January to April, and of the Furcilias from February to April. ^ From this 

 presentation of the data, in which fractional results have been disregarded throughout, it will be 

 seen that whereas in oceanic water the eggs and larvae are found down to the greatest depths 

 examined during the spawning season, the larvae in the surface ranging from the First Calyptopis to 

 the Fifth Furcilia stage,- the only substantial product of the shelf seas in the same period is that of 

 eggs alone. 



1 Strictly these ranges apply only to the northern or Weddell zone of larval abundance. They do not apply to the southern 

 or East Wind zone where the spawning is late (p. 177) and the larval growth-rate (p. 355) exceedingly slow. 



* The Sixth Furcilia (Table 43) is, of course, present as well, but in this presentation of the data appears as a fractional 

 result. 



