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Part III. — Seventeenth Annual Report 



indication in any of the figures of the main mass of eggs being as deep 

 down as 6 fathoms (except in Station II., May, and the superiority of 

 this net over the others is a slight one), but there are several cases in 

 which proportionally a considerable number of eggs were obtained at that 

 level (Station IV., March, April, and May; and Station V., July). 

 Another fact displayed by the figures is, instead of the eggs appearing 

 mainly at one level and diminishing regularly in number as they recede 

 from it, two different levels may be found well supplied with eggs, while 

 between them a much less rich region is found. This is shown at Station 

 I. in March and Station III. in June, where the intervening levels — viz., 

 1 and 2 fathoms — are respectively poorer than the levels immediately 

 above and below. Again, intervening regions may be almost destitute of 

 eggs — e.g., at 4 fathoms in Station III., February; 2 fathoms, Station V., 

 July and August. In short, so great is the diversity that it is very 

 difficult to reduce the facts to any fixed rule. One point is noticeable, 

 and that is how generally a large proportion of the eggs were found within 

 two feet of the surface. At Station V. in April, July, and August, when 

 the surface water was of low salinity — e.g., 1*52, 1*319, and 1*739 — no eggs 

 were obtained in the surface net. They were, however, found at 1 fathom. 

 This shows that the low salinity did not extend much below the surface. 

 On Station IV. in April, and Station V. in June, eggs were obtained 

 within two feet of the surface, but they were few in number. The 

 salinities in these localities were, in the months referred to, 2*31 and 

 2*75. The fact of the presence of the eggs within two feet of the surface 

 shows that the water of low salinity was confined to within less than two 

 feet of the surface. 



In Tables IV. -XI. is given the volume of Copepoda taken in each net, 

 and from these data shaded figures have been drawn on a plan similar to 

 that adopted for the eggs. The breadth of the figure at any depth is 

 proportional to the volume of Oopepods taken at that level. A glance at 

 the shaded figures shows a point in which they differ very much from the 

 figures of the egg collections — viz., in the acuteness of their apices. While 

 it was common to find a large proportion of eggs at the surface, the rule 

 in April, May, June, July, and August was that a very minute proportion 

 of Copepoda was to be found within two feet of the surface. In February 

 and March this was found to be the case on certain stations ; on most of 

 the stations in January, however, and certain stations in February and 

 March, a considerable proportion of the total amount of Copepoda was 

 found floating close to the surface. 



Station V. is a notable exception for January. On reference to the 

 Salinity Table (XVI), p. 130, the absence of Copepoda from the surface 

 would appear to be due to lower specific gravity of the surface water. 

 This is the case with regard to certain stations— viz., Station V. in January, 

 and Station IV. in April, May, June, July, and August. At the latter 

 station in May, June, and July, although the surface water was of less 

 than normal salinity— viz., 2*8, 2*49, and 2*72 per cent, of total salts — 

 the respective specific gravities being "24*6, 21*8, and 23*2 — large numbers 

 of ova were floating close up to the surface. This indicates a point of 

 great difference in the behaviour of eggs and Copepods — namely, that 

 pelagic eggs may be found in considerable numbers close to the surface 

 at a time when the surface water is of a comparatively low salinity, while 

 Copepoda are withdrawn to lower depths. A condition of lower salinity 

 does not, however, explain the absence of Copepoda from the surface on 

 all occasions. Whether this may be due to the fact that the work was 

 carried on in daylight only, is possible. It is well known, from the results 

 of the " Challenger " and other Expeditions, that the pelagic fauna sinks in 



