288 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



form from that for the juveniles. The two maxima are 

 present in each, and the apices for the adults are about 

 one month later than those for the juveniles — which is 

 very much what we should expect. Bat the numbers for 

 the adults are rather greater than those of the juveniles, 

 such as 20,000 in July as against 12,000 ; and the October 

 elevation runs up suddenly to close on 30,000, while the 

 corresponding peak for juveniles in September reaches 

 only about 10,000. It is easy from the curves to see that 

 the Nauplius population, after reduction by about one- 

 half, becomes the juvenile population ; and although it is 

 not quite so plain, still it looks probable that the juvenile 

 curve is related to that of the adults, the latter being 

 possibly reinforced in its October maximum by the 

 immigration of swarms from neighbouring seas or from 

 the North Atlantic Ocean. 



If we now take the off-shore Stat. I, and examine the 

 Copepoda in the same three stages, as caught in the fine 

 surface net, we find that during the spring period 

 (March 27th to April 26th inclusive) 19 quarter-hour 

 hauls of the net in question were taken at that locality 

 five miles off Bradda Head. The variation in the 

 numbers of the different stages present from day to day is 

 most marked in the case of the Nauplii, is less in that of 

 the juveniles, and is least in that of the adults. The 

 Nauplii run up to about 23,000 (at the end of March), the 

 juveniles to 8,000 (on April 13th), and the adults to 2,000 

 (on April 2nd and April 21st). With a more complete 

 series of statistics one could, doubtless, from the pro- 

 portions between the totals, say week by week, arrive at a 

 correct estimate of the death-rate at each stage, at the 

 different times of year. The above observations from one 

 net at one station are probably not numerous enough for 

 this purpose, but the figures given — a reduction from 



