DISTRIBUTION OF YOUNG STAGES OF EUPHAUSIA SUPERBA 113 



at a place of concentration where eggs are in somewhat shallower water than is 

 usual. 



Much more positive evidence is required on this problem before any definite solution 

 can be put forward; conclusions drawn purely from negative evidence or from out- 

 standing exceptions to the normal are very apt to be misleading, if not altogether wrong. 



TIME OF SPAWNING 



It is possible to get information about the duration of spawning in at least two ways. 

 The first by observation of adults for indication of sexual maturity, and the other by 

 consideration of the records of eggs in the plankton. It is not proposed in the present 

 paper to deal with the first method beyond referring to the spawning of females in 

 aquaria on the ship. The earliest record of this is on December 21 in the season 1930-1, 

 and it is followed by another almost a month later on January 19. The latest record of 

 eggs hatching is on February 10 in the season 1929-30. There is, then, from this source 

 evidence of spawning taking place over about seven weeks at the height of the southern 

 summer. 



Conclusions based on the presence of eggs in the plankton involve the assumption that 

 the time between the laying of eggs and the development into Naupliar and Calyptopis 

 forms is very brief. The occurrence of all stages of development up to the clearly 

 distinguishable ist Nauplius in eggs in one catch, and the fewness of ist and 2nd Nauplii 

 in any of the catches, suggest that this is probably the case. Table XXXIX shows in 

 half-monthly periods for the years 1928-31 the time at which eggs were found. 



Table XXXIX. Showing the half-monthly periods in which eggs have been found 



In the season 1927-8 there were no observations before February, but from the latter 

 half of this month there is one record of eggs. In the season 1928-9 eggs were found be- 

 tween the second half of December and the second half of February, in the 1929-30 

 season between the first half of November and the first half of February and in the 

 1930-1 season between the second half of December and the first half of March. The 

 longest period of spawning in one season is three and a half months, and for all the 

 seasons under consideration the range is four and a half months. In the 1 930-1 season 

 the station from which the first eggs were recorded was not more than 120 miles distant 



15 



