RHIZOSOLENIA CURVATA 



43' 



above, supplied one of the three records of R. curvata south of the actual position of the 

 convergence in that longitude. This station also was preceded by two days of strong 

 winds from due north, although they were not exceptionally violent. Though the 

 hydrological evidence has not yet been worked up in detail, I am informed by 

 Mr Clowes that in addition to the strong probability of direct surface drift due to these 

 unusual wind conditions, the actual position of the Antarctic convergence may have 

 been considerably south of the probable average position plotted in Fig. 4, at the time 

 when the observations in question were taken. 



• Positive records 

 O Negative records 



Fig. 4. Observations of Rhizosolenia curvata south of the Tasman Sea and in the South Pacific Ocean. 



Our findings of R. curvata on the repeated series of observations in 8o° W longitude 

 are shown diagrammatically in Fig. 5, and particulars of the stations at which positive 

 records were made will be found in Table VI. 



In Fig. 5 the probable average position of the convergence is shown by the con- 

 tinuous vertical line, and its probable actual position at the time when each individual 

 series of observations was made by the arrows. I am indebted to Mr Clowes for the 

 information upon which these positions are based, and he has asked me to state that 

 further examination of the data may show that in March 1934 the convergence should 

 have had a more northerly position assigned to it. The extreme "probable actual posi- 

 tions" are thought to represent quite fairly the extent of actual change in position of the 

 convergence during a normal year. It will be seen in Fig. 5 that the extremes were 

 reached in March and November 1934. With the aid of the meridional scale at the top 

 of the diagram it can also be seen that the distance between these extremes is not great, 

 barely 2 of latitude. 



The observations in longitude 8o° W present several features of special interest from 



